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August 2 

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Vol. 40 • Issue 8 

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Will Curiosity find 

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The Mars Science 
Laboratory, called 
Curiosity, should 
land on the Red 
Planet on August 
6. It will explore 
Gale Crater for 
signs of past and 
present life. 

August 2012 

20 Will Curiosity find life 
on Mars? 'iV 

NASA's Mars Science Laboratory 
mission packs the most advanced 
suite of scientific instruments ever 
sent to another world. JIM BELL 


How twin rovers found 
water on Mars W 

In 2004, NASA landed two robot 
geologists on Mars, hoping to get 90 days 
of work out of them. After eight years 
of exploration, Spirit and Opportunity 
have deepened our knowledge of the 

34 Illustrated: How we'll get to Mars 

Landing humans on the Red Planet will be difficult and dangerous — but it can be done. 

36 The Sky this Month 

Neptune shines at its brightest. MARTIN RATCLIFFE AND ALISTER LING 

38 StarDome and Path of the planets 


44 The Red Planet's colorful past'* 

Since antiquity, Mars has captured our minds and imaginations, 
and its study has led to important discoveries — and some of the 
greatest misconceptions — in planetary science. KARRI FERRON 

50 Ask Astro 

Rocks from space. 

52 Imaging heaven and Earth 9 

Astrophotographer wally pacholka lias made an art of capturing amazing landscapes and 

58 Explore the Summer Triangle 

Although you'll never see Mars within the area bounded by these three bright stars, 
you can explore double stars, nebulae, and star clusters. MICHAEL E. BAKICH 

60 20 best dark-sky sites in the U.S. 

Searching for a place to set up your telescope? A top-notch location might be closer 
than you think. MICHAEL E. BAKICH 

62 Astronomy tests Vixen's compact astroimaging mount 

The Polarie Star Tracker makes it easy to take long-exposure wide-field images. 




10 Strange Universe 

Space: women needn't apply? 

11 Secret Sky 

The mystery of 
daylight aurorae. 

64 Observing Basics 

Accessible astronomy. 


65 Imaging the Cosmos 

"HDR Toning," part 2. 



6 This Month in Astronomy 

Truth and science. 

8 Letters 

Great tip. 

9 Web Talk 
12 Astro News 

Gamma-ray bursts not 

responsible for extreme 

cosmic rays. 

A longer Late Heavy 


Astro Confidential: 

Kate Rubin. 

66 Deep-sky Showcase 

67 New Products 

70 Advertiser Index 

71 Reader Gallery 
74 The Cosmic Grid 

Astronomy (ISSN 0091-6358, USPS 531-350) is 
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This Month in Astronomy AStrOflOITIV 

Truth and science 

by David J. Eicher 

Recently, I saw a clip of an Arizona 
state senator arguing for uranium 
mining in her state in part because 
"Earth is 6 thousand years old." Using 
radioactive elements like the very uranium 
she was talking about, we know that Earth 
is 4.5 billion years old. It's staggering that 
we have such ignorance in the year 2012. 

It does raise the point about the rela- 
tionship between science and truth. Just 
what means do people use to determine 
what is true and what is false? Lets examine 
them from the worst to the best. 

Intuition is highly subjective and pre- 
ferred by theologians. It relies on guess- 
work, dreams, imagination, inspiration, 
revelations, and visions, and may have no 
basis whatsoever in reality. Ancient phi- 
losophers considered intuition "self- 
evident" unless they were faced with oppos- 
ing viewpoints. In this case, they simply 
declared the opposition false, heretical, 
demented, or blasphemous. If I started 
believing that everything in my dreams 
were true, well, let's just say it would be a 
more interesting world than it really is. 

Authoritarian methods are derived 
from expert testimony from parents, sib- 
lings, relatives, friends, neighbors, teachers, 
clergy, politicians, and celebrities. This kind 
of truth is reinforced by sheer repetition. 
It's the knowledge we grow up with and 
becomes so-called common sense. Why 
should we believe it? Ya know, because 
this guy said it! 

Rational methods use formal deduc- 
tions based on logical constructs and math- 
ematical procedures. These involve things 
like probability, casual interpolations, anal- 
ogies, semantics, statistics, and syllogisms. 
Although mathematical methods of deter- 
mining the truth are far more reliable than 
dreams or what some guy happens to tell 
you, they still have their limitations. 

Empirical methods have always been 
favored by scientists. These methods use 
careful observations and experiments to 
document the truth in a repeatable way by 
uncoerced investigators. When the force of 
gravity on Earth has been measured a hun- 
dred million times by hundreds of thou- 
sands of people over the past several 
centuries and they all get the same answer, 
it gives you good confidence it's the truth. 

The usual criticism of empirical meth- 
ods is that coincidental observation does 
not lead immediately to firm, dependable 
conclusions. But that's exactly what makes it 
strong and reliable! The truth as we best 
know it is always continuously being 
altered or improved upon on smaller and 
smaller scales by later discoveries and 
observations. Scientific knowledge is in a 
state of continual refinement. 

So be patient with science, and trust it to 
provide the best truth of the cosmos 
around you. Save your dreams for fun and 
fantasy. If that guy tells you something is so 
because he says it's so, have the indepen- 
dent ideas to challenge him. Get the truth 
at the source, where humans have found it 
in the best and most reliable way for half a 
millennium — observational science. 

Yours truly, 

Volume 40, Number 8 

Editor David J. Eicher 

Art Director LuAnn Williams Belter 


Senior Editors Michael E. Bakich, Richard Talcott 

Associate Editors Bill Andrews, Liz Kruesi 

Assistant Editor Karri Ferron 

Editorial Associate Valerie Penton 


Senior Graphic Designer Alison Mackey 

Illustrator Roen Kelly 

Production Coordinator Annie Guldberg 


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David H. Levy, Alister Ling, Steve Nadis, Stephen James 
O'Meara.Tom Polakis, Martin Ratcliffe, Mike D. Reynolds, 
Sheldon Reynolds, John Shibley, Raymond Shubinski 


Buzz Aldrin, Marcia Bartusiak, Timothy Ferris, Alex Filippenko, 
Adam Frank, John S. Gallagher III, Daniel W. E.Green, William K. 
Hartmann, Paul Hodge, Anne L. Kinney, Edward Kolb, 
Stephen P. Maran, Brian May, S. Alan Stern, James Trefil 

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Follow Astronomy 

6 Astronomy-August 2012 





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8 Astronomy -August 2012 


We welcome your comments. Send letters to Astronomy Letters, 
P. O. Box 16 12, Waukesha, Wl 53187; email to letters@astronomy. 
com. Please include your name, city, state, and country. Letters 
may be edited for space and clarity. 

Great tip 

I can't begin to tell you how much 
Senior Editor Michael E. Bakich's 
"Wander winters deep sky" (Decem- 
ber 201 1) influenced me. Before reading 
the article, I was already working on a 
design for the next telescope I will build. 
It will be a replacement for my 17.5-inch 
Dobsonian, which has become too 
heavy for my ailing back and joints to 
manage. So, after waffling back and 
forth between 12.5 and 14.5 inches, I 
settled on the safer choice of 12.5 inches. 

Ah, but enter Bakich. After reading 
his article, I saw that I couldn't get past 
Thor s Helmet (NGC 2359) with that 
aperture. It didn't take long for me to 
switch to a 14.5-inch mirror and stay 
switched. I plan to have my newest 
scope see first light at the Wisconsin 

Exactly what I thought 

I am so busy that I rarely comment on any- 
thing I read, but I stopped everything I was 
doing to write to Astronomy after reading 
an article in your magazine. I don't think 
anyone, including me, could have written 
their opinions as clearly, completely, or elo- 
quently as Brian May did in "What are we 
doing in space?" (February 2012). This 
gives me hope that there are a lot of us who 
agree with his statements. I thank you, 
Brian May, for being so honest and to the 
point, and speaking my mind as well as 
yours. And thank you, Astronomy, for being 
brave enough to print it! This article alone 
is worth far more than a lifetime of sub- 
scription costs, even if you never printed 
another word. — S. A. Leonard, Ocala, Florida 

Bettering science education 

With all the recent discussion of science 
education, I wanted to mention a program 
we have in India that is successful at identi- 
fying talented young scientists with an 
interest in astronomy. The National Astron- 
omy Olympiad Programme encourages 
students with good foundations in physics 
and mathematics and an interest in astron- 
omy to pursue further studies. 

New parts for a 14.5-inch scop became 
necessary for reader Steve J. B. Bouton after 
reading Senior Editor Michael E. Bakich's 
"Wander winter's deep sky" (December 
201 1 ); his plan for a 1 2.5-inch telescope 

WOUld nO longer dO. SteveJ.B. Bouton 

Observers Weekend in July. Thank you 
for helping me come to my senses. 
— Steve J. B. Bouton, Evanston, Illinois 

Some 15,000 students are initially 
invited to apply to represent India in the 
International Olympiad in Astronomy and 
Astrophysics (IOAA). After undergoing 
two exams based on physics, mathematics, 
and a bit of general astronomy, we narrow 
the list down to about 35 senior students 
and 20 junior students. We then invite 
them to participate in a 20-day astronomy 
workshop, and from that group we select 
five students to represent India at the 
IOAA and three for the International 
Astronomy Olympiad. 

Of the 55 students we've sent to the com- 
petitions over the past 10 or so years, 42 are 
pursing astronomy, physics, chemistry, biol- 
ogy, or mathematics for their careers. We 
believe that the program has done well in 
identifying and encouraging talented stu- 
dents to pursue a career in science. 
— Suhas B. Naik-Satam, Nehru Planetarium, Mumbai, India 


In the time line at the bottom of page 33 of 
the article "What has astronomy done for 
you lately?" (May 2012), FFT should be an 
abbreviation for "Fast Fourier Transform," 
not "Fast Fourier Transfer." We apologize 
for the confusion. — Astronomy Editors 

^Q Web Talk 

What's by Karri Ferron 

A community 
on the go 

More features on go mobile 

It's easier than ever to stay connected with your 
astronomy community. Astronomy's mobile site 
now lets you chat in the forums, check out the 
latest images in the Reader Photo Gallery, com- 
ment on staff blog posts, and more — all from 
your smartphone or tablet. Just click on the 
"Community" tab, log in with the same registra- 
tion information you use on, 
and you'll have access to all of your private con- 
versations, active forum threads, and astropho- 
tos. With this update, sharing highlights of your 
observing session can happen in real time, and you no longer have to 
wait until you have access to a computer to ask that burning cosmolog- 
ical question. Bring the community with you every- 
where you go using 




Weekly podcast 

Each week, Astronomy Senior Editor Michael E. Bakich records a pod- 
cast featuring three or more objects you can see in the night sky in the 
next seven days: At least one of them you can find through a small 
telescope, and two or more are deep-sky targets to seek out with an 
8-inch or larger instrument. For each, Bakich provides detailed observ- 
ing information, interesting historical anecdotes, and other fun facts. 
Registered users, check back each Thursday to see what objects he'll 
highlight next at 


Reader Photo Gallery 

Submit beautiful astroimages like 
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numerous gallery catalogs, including Galaxies, Nebulae, Stars and Star 
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Comment on photos and learn from other imagers' techniques. Begin- 
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by Bob Berman 

Space: women needn't apply; 


Debra Elmegreen challenges astronomy's anti-female legacy. 

Let's do something different and 
tackle a sociologically odd topic. It's 
the shameful fog that blanketed our 
beloved astronomy for centuries — the 
exclusion of women. 

Take Maria Mitchell (1818-1889), 
America's first female professional astrono- 
mer. If you're ever on the enchanted island 
of Nantucket off the coast of Massachusetts, 
you can visit her old house and observa- 
tory, where she became instantly famous in 
1847 by discovering a comet. It's hard not 
to love this long-gone woman who wrote, 
"Standing under the canopy of stars ... you 
could scarcely do a petty deed." 

Her story had a rare happy ending as she 
became the very first professor at a brand 
new college named Vassar. But few others 
fared as well. Annie Maunders (1868-1947) 
acute mind played a big behind-the-scenes 
role in the success of 19th-century solar pio- 
neer Edward Maunder when the British cou- 
ple clarified the 1 1-year sunspot cycle. Yet, 
despite being voted mathematician of the 
year at Cambridge University and passing 
her final qualifying exam, she was denied a 
degree simply because she was a woman. 

Such discrimination continued. At the 
famous 200-inch Hale Telescope on Palo- 
mar Mountain in California, women were 
simply not welcome. And when Jocelyn 
Bell Burnell discovered pulsars in 1967, the 
revelation won a Nobel Prize — for her 
research advisor, who did little of the work. 
Burnell wasn't even mentioned. 

Into this disgraceful legacy came Debra 
Meloy Elmegreen. Now completing her 
two-year presidency of the American 
Astronomical Society (AAS), this woman 
represents our nation's professionals. 

I've interviewed many of our top brilliant 
women, like the Carnegie Observatories' 
Wendy Freedman and planetary guru Heidi 
Hammel, and wish I had crossed paths with 
Vera Rubin, now in her 80s, famous for her 


Browse the "Strange Universe" archive 

Debra Meloy Elmegreen is an astronomy 
professor at Vassar College in Arlington, New 
York, and president of the American 

Astronomical Society. Debra Meloy Elmegreen 

groundbreaking dark- matter work even 
though she couldn't get into Princeton's 
graduate program because it was men only. 
But I'll let Elmegreen serve as sort of our 
breakthrough woman astronomer. 

It's really an excuse. Fact is, I adore her. 
Everyone does. That's possibly why she was 
selected as the first-ever AAS president 
from a small college. Being likeable counts. 

She also has guts. Maybe 15 years ago, I 
invited her to be my guest on a radio call-in 
show, and she agreed even though it meant 
flying 45 minutes to another city in my 
beat-up four-seat hippie plane. So, this 
first-ever "Strange Universe" bio has a dual 
purpose: first, to do my part to help erase 
that terrible an ti- woman astro -legacy; and 
second, to salute the person who has been 
the official spokesmammal for American 
astronomers since 2010. 

Elmegreen grew up in Fairfax, Virginia. 
As a teenager, she ground her own telescope 
mirror and built a 16-square-foot (1.5 square 
meters) shortwave receiver to study Jupiter. 
She then wrote an article for this magazine 
("Tuning In On Radio Astronomy: Building 
Your Own Radio Telescopes," December 
1977) and won all sorts of Westinghouse and 
other science fairs. The consummate geek, 

she'd hold star parties in her backyard. The 
magazine Seventeen decided to do an "Up 
and Coming Teen" feature on her, but when 
they asked Elmegreen for her astrological 
sign and whether Jupiter was in her horo- 
scope, she disclaimed that nonsense, so the 
publication killed the article. 

No matter. She got her bachelor's degree 
in astronomy from Princeton University 
— the first woman to do so — and then her 
master's and doctorate from Harvard. "In 
those rare moments of total quiet with a 
dark sky, I again feel the awe that struck me 
as a child," she says. "I enjoy observing gal- 
axies at optical, infrared, and radio wave- 
lengths, and hope to contribute more to the 
understanding of galaxy star formation and 
structure in galaxies." 

She already has. As Vassar s Maria Mitch- 
ell Professor of Astronomy, she often uses 
the Hubble Space Telescope and is especially 
focused on colliding galaxies and how their 
structure in the early universe is so different 
from those today. It was she who coined the 
term flocculent galaxy for bizarre ones like 
NGC 7793 that have many short chaotic 
arms instead of the two elegant spirals dis- 
played by "grand design" galaxies. 

Despite her research workload, she 
teaches five courses a year at Vassar, while 
her duties as AAS president take her to 
places like Congress and the Vatican. 

When the movie Thor came out starring 
Natalie Portman as an astrophysicist, a mag- 
azine cited Elmegreen as the real-life model. 
Indeed, the portrayal of fictional female 
astronomers like comet-observing Darryl 
Hannah in the film Roxanne and alien- 
searching Jodie Foster in Contact shows 
how far we've recently come. Although just 
22 percent of professional astronomers are 
women, for the under-30 pool the number 
has now grown to 40 percent. 

For the moment, though, I guess we can 
live with "the man in the Moon." <* 

Contact me about my strange universe by 

10 Astronomy -August 2012 



by Stephen James O'Meara 

The mystery of daylight aurorae 

Can these nighttime light shows compete with the Sun's glare? 

Aurorae, the northern and southern 
lights, are one of the night sky's most 
i animated spectacles. Some even 
splash their colors across twilit skies. But has 
anyone ever seen an aurora in the daytime? 

On October 25, 1870, observers across 
the British Isles witnessed a brilliant crim- 
son display, which apparently began at 
about 5:30 p.m. (some 50 minutes after sun- 
set). A couple of months later, in a letter 
published in the December 8, 1870, issue of 
Nature, James Cubitt reported that he first 
spotted activity from Huntingdonshire at 
4:30 p.m. (about 10 minutes before sunset). 

Cubitt described the daylight activity as 
a "remarkable pale luminous appearance" 
some 25° above the eastern horizon, where 
he saw "two arcs of faint white lines, one 
above the other, both radiating outwards 
with a number of short points." He added 
that the sighting interested him because "it 
seems that the greatest disturbance of the 
telegraphs happened before the evening 
display of the aurora." 

The letter brought swift criticism. In the 
next issue of Nature (the following week), 
George F. Burder said he ventured "to 
believe not" Cubitt's and others' similar 
claims. After reviewing historical cases, Bur- 
der concluded that all such daylight sight- 
ings suffer from "errors of observation." In 
Cubitt's case, he suspected that the "object 
observed was nothing more than a remark- 
ably symmetrical form of cirrus cloud." 

The debate continued into the following 
year with W. G. Thompson recalling, in the 

Faint auroral activity during twilight, such as 
this wispy example the author captured over 
Iceland, shows just how difficult the ethereal 
lights would be to see against a daylit sky. 

The aurora borealis, or northern lights, is one of the most dazzling sights of the night sky. 
But could the most intense displays glow strongly enough to be visible in the daylight? 

March 2, 1871, issue of Nature, a brilliant 
auroral display in 1870 that, "beyond a 
doubt," could be seen in the daylight. "In the 
autumn of last year," he wrote, "my eye was 
attracted by an unusual motion, in what at 
the first glance appeared to be a light fleecy 
cloud, but was in reality a broad ribbon of 
Aurora of a yellowish white colour, which 
changed its form and position with the 
peculiar streaming motion of the Aurora, 
sometimes almost fading entirely and again 
recovering its comparative distinctness." 

John Jeremiah also disagreed with Bur- 
der, and in a May 1871 issue of Nature set 
out "to prove the fallacy of such reasoning," 
by sharing with readers nine historical 
accounts of daytime aurorae he found dat- 
ing from a.d. 1122 to 1871. 

Personal finds 

Several years ago, while conducting unre- 
lated research at the Boston Public Library, I 
found two additional claims of daylight 
aurorae sightings. The first dates to 1786 and 
occurred during a Danish expedition to the 
Arctic. As Sir John Barrow described in his 
1818 work, A Chronological History of Voy- 
ages into the Arctic Regions: "A phenomenon 

was observed during the day-time which 
[the captains of the two ships involved] con- 
cluded to be the aurora borealis." The activ- 
ity consisted of "streaks of light columns and 
luminous points" shooting up from the hori- 
zon, "darting and changing their shapes in 
the same maimer as [an aurora]." They saw 
the same phenomenon the following day, 
but more faintly. "If it was the aurora borea- 
lis," Barrow wrote, "it is probably the first 
time it has been observed by daylight, and 
when the sun was above the horizon." 

The second claim appeared in Sir John 
Franklin's 1824 Narrative of a Journey to the 
Shores of the Polar Sea, in the Years 1819, 20, 
21, and 22. In an appendix, he included this 
extract from Dr. John Richardson's journal: 
"March 8, 1821. At 6 p.m, before the daylight 
was gone, the Aurora appeared ... stretching 
up towards the zenith. At seven, two faint 
arches crossed the zenith. The Aurora was 
bright and copious all the evening." 

If you have a daytime aurora experience 
of your own you'd like to share, please let 
me know at » 


Browse the "Secret Sky" archive at 1 1 

V August2012 

App-reciate it! 

As of April 3, fans of NASA's Kepler mission could download Kepler Explorer, 
a free app showcasing the discoveries of the planet-hunting quest. 

For the latest news on 

space discoveries, 

spacecraft missions, 

and sky events, visit 


Gamma-ray bursts not responsible 
for extreme cosmic rays 

Particle shower. The search for the source of ultra-high- 
energy cosmic rays has led to scientists crossing off one 
leading theory: Gamma-ray bursts do not rev up these 
particles to their extreme energies. NSF/j.vang 

Ever since scientists discovered ultra- 
high-energy cosmic rays (particles from 
space) in the mid- 19th century, they've 
been searching for what revs up these 
particles to such extreme energies. The- 
ories proposed that either the explosive 
death of an extremely massive star 
(resulting in a gamma- ray burst [GRB]) 
or jets shot out from supermassive black 
holes could accelerate cosmic rays to 
energies 1 million to 1 billion times 
those created in the largest Earth-based 
accelerators. Now, a study published in 
the April 19 issue of Nature suggests that 
GRBs are not responsible for ultra-high- 
energy cosmic rays, thus ruling out one 
of the leading possibilities. 

The team analyzed data from Ice- 
Cube, a cubic-kilometer detector 
embedded in the Antarctic ice. The 
IceCube collaboration looked for neu- 
trinos — particles that interact weakly 
with matter and have little mass — that 

are produced as ultra-high-energy 
cosmic rays decay into other particles. 
The researchers compared the posi- 
tions of more than 200 GRBs to Ice- 
Cube neutrino data. 

"According to a leading model, we 
should have expected to see 8.4 events 
corresponding to GRB production of 
neutrinos in the IceCube data," says 
Spencer Klein of the Lawrence Berke- 
ley National Laboratory in California 
and a member of the IceCube collabo- 
ration. "We didn't see any, which indi- 
cates that GRBs are not the source of 
ultra-high-energy cosmic rays." 

Ruling out one method does not 
confirm that the other leading theory 
(jets from active supermassive black 
holes) is the answer to this decades-old 
puzzle. Scientists will use IceCube and 
other particle detectors to continue 
searching for the cause of ultra-high- 
energy cosmic rays. — LIZ kruesi 

In 2006, scientists discovered the Bullet 
Cluster, the first galaxy cluster merger 
found where normal matter was 
wrenched from dark matter — material 
that doesn't emit any light or radiation 
but can be detected through gravitational 
ensing. Since then, astronomers using 
NASA's Chandra X-ray Observatory have 
uncovered six similar examples, the most 
recent one released April 12. The newly 
discovered Musket Ball Cluster, named so 
because it is older and slower than the 
Bullet, is about two to five times further 
along in the merger process than previ- 
ously observed systems. — KARRI FERRON 

12 Astronomy -August 2012 

Dawn relays 
results from Vesta 

After more than nine months orbiting the giant 
asteroid Vesta, NASA's Dawn spacecraft is paint- 
ing a better picture of the second-most massive 
object in the main asteroid belt. In a presentation 
at the European Geosciences Union meeting in 
Vienna, Austria, on April 25, scientists revealed 
new data about Vesta's surface composition, 
internal structure, and temperature fluctuations. 

Images from the spacecraft's visible and infra- 
red mapping spectrometer show a variety of sur- 
face minerals and rock patterns. Many features 
are composed of iron- and magnesium-rich min- 
erals, similar to the composition of earthly volca- 
nic rocks. Dawn also revealed an area of banding 
near a south pole crater; it shows contamination 
from space rocks bombarding Vesta in layers 
closer to the surface and more original character- 
istics of the asteroid in layers below. 

"These results from Dawn suggest Vesta's 'skin' 
is constantly renewing," says Maria Cristina De 
Sanctis, lead of the visible and infrared mapping 
spectrometer team based at Italy's National Insti- 
tute for Astrophysics in Rome. 

In addition to imaging, Dawn has made 
extensive ultrasensitive measurements of Vesta's 
gravitational influence on the spacecraft, which 
give researchers clues about the asteroid's 

Colorful crater. 

The comparatively fresh impact 
crater Vibida on Vesta shows a colorful blanket 
of ejecta material in this composite false-color 
image. The different kinds of materials reflect a 
complex interplay between ancient volcanic and 
impact processes that shaped the asteroid's 


unusual densities within its outer layers. Scien- 
tists also have created the highest-resolution sur- 
face temperature maps of any asteroid. Dawn's 
data reveal that Vesta can vary in temperature 
from -10° Fahrenheit (-23° Celsius) to at least 
-1 50° F (-1 00° C), or the lowest reading the 
spacecraft can record. 

Because of Dawn's success so far, NASA 
announced April 1 8 that the spacecraft will 
spend an extra 40 days at Vesta, until August 26, 
before departing for its scheduled arrival at the 
dwarf planet Ceres in February 201 5. — K. F. 

A young cluster's heated environment 

The stellar cycle. Winds and radiation from a cluster of young stars near the upper left of this image push 
stellar material into a compact region, thus encouraging the next generation of stars to form. This cluster, 
NGC 6604, lies about 5,500 light-years away in the constellation Serpens the Serpent. Astronomers also see a 
perplexing column of hot gas extending 650 light-years above the hot young stars, but they don't understand 
the structure's formation. The European Southern Observatory released this image April 25. — L. K. eso 


NASA announced April 13 
that its Swift satellite visu- 
ally captured Comet C/2009 P1 
(Garradd) on its path away from 
the Sun and would continue to 
track its journey. 


NASA announced April 5 that 
it had extended the orbiting 
Kepler and Spitzer missions for 
two years, and its involvement in 
the Planck mission one year. 


Officials named a recent super- 
nova and a massive database of 
astronomical data in honor of 
U.S. Senator Barbara Mikulski, 
NASA announced April 5. 


The Giant Magellan Telescope 
Organization's board of direc- 
tors announced April 2 that 
they would not seek funds 
from the National Science 
Foundation (NSF). 


Researchers have discovered the 
two oldest known white dwarf 
stars just 100 light-years away, as 
detailed in an upcoming paper 
in the Monthly Notices of the 
Royal Astronomical Society. 


Lockheed Martin announced 
April 16 that it had completed 
building the Near Infrared 
Camera for the upcoming James 
Webb Space Telescope, due to 
launch in 2018. 


Planetary scientist and author 
David H. Grinspoon will be the 
first Baruch S. Blumberg NASA- 
Library of Congress Chair in 
Astrobiology, the space agency 
announced April 16. 


NASA announced April 19 that it 
had successfully transferred the 
space shuttle Discovery to the 
Smithsonian National Air and 
Space Museum. 


Studies of microbial life beneath 
asteroid craters on Earth indicate 
that life may exist beneath Mars' 
craters as well, according to an 
April 2 paper in Astrobiology. 


Chinese astrophysicist and 
human rights advocate Fan Lizhi 
of the University of Arizona in 
Tucson passed away April 6 at 
the age of 76. — BILL ANDREWS 

^Q Astronews 


Old and brimming. The elliptical NGC 41 50 
is one of 260 galaxies astronomers studied 
to learn about the distribution of low-mass 
compared to high-mass stars, which can tell 
them about galaxy evolution. 

Early galaxies 
formed stars 

To understand galactic evolution, astrono- 
mers need to know about galaxies' con- 
tents and their distribution of stars of 
varying masses. For decades, scientists have 
argued whether the ratio of low-mass stars 
to massive stars is consistent among differ- 
ent types of galaxies. A new analysis of 260 
galaxies that formed early in the universe, 
and thus are called "early" ellipticals and 
lenticulars (these have disk components, 
but are older than spiral types), points to 
variations in the stellar distribution: Massive 
old elliptical galaxies have a larger fraction 
of low-mass stars. The findings appeared in 
the April 26 issue of Nature. 

Led by Michele Cappellari of the Uni- 
versity of Oxford in England, the astrono- 
mers measured the motions of stars 
compared to their positions to determine 
the mass distribution of the galaxies. They 
then measured the emitted light of those 
galaxies and compared the calculated 
mass to luminosity. The team also elimi- 
nated the possibility that the additional 
mass is from a mysterious invisible mate- 
rial called dark matter. 

The overall trend showed that these 
early galaxies contain more mass — and 
thus, more low-mass stars — than a univer- 
sal stellar distribution would assume. The 
finding implies that star evolution and for- 
mation, and therefore galaxy evolution, dif- 
fered in the early universe. — L. K. 

A longer Late Heavy 

A few hundred million years after our solar 
system's planets formed, a barrage of aster- 
oids pummeled Earth and the Moon. Scien- 
tists believe this period, known as the Late 
Heavy Bombardment (LHB), lasted from 
roughly 4.1 to 3.8 billion years ago. How- 
ever, in two Nature papers published online 
April 25, researchers discuss a method to 
investigate the record of Earth's impact his- 
tory and outline the evidence for a longer 
bombardment period. 

Because Earth's tectonic processes and 
surface weather phenomena destroy the evi- 
dence of asteroid impacts (craters), scientists 
use the Moon's impact history as a guide for 
our planet's past. This is how they learned 
about the LHB period. 

From crater studies, researchers know 
that incoming asteroids have huge amounts 
of energy due to their mass and high 
speeds. Thus, instead of digging out a 
trench in the material it hits, the asteroid 
explodes, vaporizing itself and the target 
rock. Once the vapor plume cools, it con- 
denses into millimeter-sized droplets called 
spherules. These droplets fall to the ground, 
and the millimeter- to centimeter-sized layer 
is preserved in rock. Scientists know of 14 of 
these rock layers scattered across Earth. Four 
date to between 3.47 and 3.24 billion years 
ago; seven to between 2.63 and 2.46 billion 
years ago; one to 1 .85 billion years ago; and 
two from tens of millions of years ago, 
including the K/T impact that led to the 
extinction of the dinosaurs. All of these lay- 
ers indicate that huge collisions occurred in 
those time frames. 

From the thickness of the spherule lay- 
ers, Jay Melosh and Brandon Johnson of Pur- 
due University in West Lafayette, Indiana, 
estimated the sizes and speeds of the aster- 
oids that led to the molten-rock droplets. 
They calculated that most of the space rocks 
were substantially larger than the one 
responsible for the K/T transition. These 
results suggest that the LHB did not 
abruptly end 3.8 billion years ago, as 
suspected, but instead gradually declined 
through about 2 billion years ago. 

The other study offers an explanation for 
a much longer LHB period. William Bottke of 
the Southwest Research Institute in Boulder, 
Colorado, and colleagues say the impactors 

Telling rock. A sample from a layer of mineral 
inclusions in rock found in Western Australia 
dates to about 2.63 billion years ago. By 
analyzing this and 13 other spherule layers 
across Earth, scientists estimated the size and 
speed of impacting asteroids and suggest that 
the Late Heavy Bombardment period lasted 
until around 2 billion years ago. Bruce 

came from an extended portion of the inner 
asteroid belt, which they call the"e-belt." 

Planetary scientists' leading theory of the 
early solar system fits observations — such as 
the planets' current orbits and the LHB period. 
This "Nice model" says that the giant planets 
began closer to the Sun, but about 4 billion 
years ago Jupiter and Saturn passed through 
an orbital resonance that caused chaos in the 
solar system. This gravitational shift pushed 
the orbits of Uranus and Neptune farther out 
and into a region of space rocks. These com- 
ets and asteroids went flying into the inner 
solar system and slammed into Earth and the 
Moon (along with the other inner worlds). 

Bottke's team performed simulations of 
the Nice model with an inner e-belt between 
1 .7 and 2.1 astronomical units (where 1 
astronomical unit is the current average 
Earth-Sun distance). In this model, asteroids 
pummeled Earth and the Moon for a longer 
period, extending the LHB to some 2 billion 
years ago and supporting the time frame 
that Melosh and Johnson found with their 
spherule-layer analysis. — L K. 

14 Astronomy -August 2012 

Disappearing dark matter. This artist's 
concept depicts the expected distribution of 
dark matter (in blue) around the Milky Way 
Galaxy. New findings, however, suggest that 
the mysterious substance may not be as 
prevalent after all. eso/l. ca^da 

Lack of dark matter 
surprises scientists 

Dark matter sure isn't making things easy for 
scientists. They had expected the area around 
our Sun to be full of the stuff, but an upcom- 
ing paper in The Astrophysical Journal reveals 
that our galactic neighborhood is dark matter 
free. Not only does this contradict the current 
understanding of how galaxies form and 
behave, but it also likely dooms earthbound 
searches for the elusive substance. 

"Our calculations show that it should have 
shown up very clearly in our measurements," 
says lead author Christian Moni Bidin of the 
University of Concepcion in Chile. "But it was 
just not there!" The hypothetical substance 
accounts for about 80 percent of the uni- 
verse's matter and interacts only through the 
force of gravity, rendering it almost perfectly 
invisible. By studying the movements of stars 
and other objects, astronomers can infer the 
presence of dark matter, despite being 
unable to explain it. 

But the new findings, derived from the most 
accurate analysis yet of stellar motion within 
13,000 light-years of the Sun, contradict expec- 
tations. Rather than bursting with dark matter, 
the area is almost entirely devoid of it. Only an 
unlikely distribution of the substance in the 
Milky Way can explain this outcome while keep- 
ing current models intact. Further, the lack of 
dark matter in our vicinity makes any attempts 
on Earth to detect it unlikely to succeed. 

Unfortunately, the new results don't erase 
the original need for the theoretical matter to 
explain galactic behavior, either. "If dark mat- 
ter is not present where we expected it, a new 
solution ... must be found," says Moni Bidin. 
"The mystery of dark matter has just become 
even more mysterious." — B. A. 

Nov. 16,2011 

Nov. 29, 2011 

Uranus aurorae 

White lights. For the first time, 
scientists using the Hubble Space 
Telescope glimpsed Uranus' aurorae, a 
result of charged particles from the Sun 
colliding with molecules in the planet's 
atmosphere. The aurorae appeared 
far from the poles because Uranus' 
magnetic field is inclined 59° to its spin 
axis. The images appeared in the April 
14 Geophysical Research Letters. — K. F. 

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^Q Astronews 

Imnir imnartc Asteroids acquired their "iron-loving" elements — a heavy class that bind tightly to 
II Ul IK 11 1 1 pa 11 J j ron — through impacts, just like Earth, according to an April 6 paper in Science. 


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Up close star formation 

Hooray, Hubble! When the Hubble Space Telescope has a birthday, we all get a present. In honor of 
the orbiting observatory's 22nd year in space, the Hubble team released this scene of unruly star 
birth April 1 7. Some 1 70,000 light-years away in the Large Magellanic Cloud, one of the Milky Way 
Galaxy's irregular neighbors, lies the Tarantula Nebula, and within it this region known as 30 
Doradus. This area hosts the most massive stars ever seen, and, appropriately, this image represents 
one of the largest composites ever created from Hubble photos. — B. A. 

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New insights into 
stellar death 

Whether in humans or stars, death is a big — 
and largely unknown — part of the life cycle. 
A Nature study published April 1 2 may start to 
change that, however, as it describes events 
surrounding the demise of Sun-like stars in 
unprecedented detail. "We are now a big step 
further in understanding this cycle of life and 
death," says co-author Albert Zijlstra of the 
University of Manchester in England. 

When intermediate-mass stars like the Sun 
reach the red giant phase at the end of their 
lives, they begin to emit a "super wind" millions 
of times stronger than ordinary stellar wind. 
Over some 10,000 years, this process removes 
about half of the star's mass, but astronomers 
weren't sure exactly how it worked. They had 
suspected that the uppermost stellar layers 
formed tiny dust grains, which the star's radia- 
tion then pushed outward. The problem was 
that such grains would theoretically burn up 
before traveling far. 

The researchers solved this mystery by 
studying three red giants at exceptionally high 
resolution. They found surprisingly large dust 
grains (about 600 nanometers across) less 
than a stellar diameter away from each giant, 
suggesting that the dust didn't absorb the 
star's light directly, instead likely reflecting it. 

Not only does this explain the super wind's 
behavior, and thus shed light on how stars like 
our Sun will one day die, but it also helps sci- 
entists understand how planets like Earth 
form. "The dust and sand in the super wind 
will survive the star and later become part of 
the clouds in space," says Zijlstra. "Our own 
Earth has formed from star dust." — B. A. 

Death throws. Middleweight stars like our Sun 
eventually will become red giants, as depicted 
in this illustration. Scientists have recently 
figured out a way to explain how these 
behemoths can spew out much of their mass 
without it burning up in the process. D,,,d a, IUI i.„ oa 

16 Astronomy -August 2012 

Focus: Fomalhaut. 

Nearby Fomalhaut, the 
young star near the center 
of this image, likely has 
two planets orbiting on 
either side of a cool dusty 
ring made up of debris 
from the collisions of 
comets. Here, the latest 
radio emissions (in orange) 
appear overlaid on visible- 
light observations (in blue). 

120 SUNS 

The light output of the 

surprisingly dim star 

ter Munoz 1, according 

I an upcoming paper 

in The Astrophysical 

Journal Letters. 

planetary system 

Fomalhaut may not yet be a household 
name, but perhaps that's just a matter of 
time. Two recent scientific papers describe 
the young star's dynamic system, including a 
dust ring built from thousands of daily come- 
tary crashes and two small planets embed- 
ded within the ring. 

The first paper, published online April 1 1 by 
Astronomy & Astrophysics, describes the com- 
position of the dusty ring around Fomalhaut, a 
star twice as massive as our Sun about 25 
light-years away. The extremely cold tempera- 
tures within the ring, combined with earlier 
observations, suggests that fluffy assemblages 
of dust released from cometary collisions make 
up its bulk. Because the star would soon blow 
away the debris from these crashes, the 
authors speculate that tremendous numbers 
of daily collisions — enough to pulverize 2,000 
comets about 0.6 mile (1 kilometer) across — 
keep the supply of dust high. "I was really sur- 
prised," says lead author Bram Acke of the 
University of Leuven in Belgium. "To me, this 
was an extremely large number." 

Second, a May 1 paper in The Astrophysical 
Journal Letters focuses on two planets that 
straddle the dust ring as they orbit Fomalhaut. 
In fact, it was the sharp edges of the dust ring 
that allowed the researchers to confirm the 
planets' presence and even determine some of 
their characteristics. "The masses of these plan- 
ets must be small," says lead author Aaron 
Boley of the University of Florida in Gainesville. 
"Otherwise, the planets would destroy the ring." 
Previously, astronomers had suspected that a 
single larger planet orbited Fomalhaut. 

This latter discovery is also significant 
because it's the first published science find- 
ing from the Atacama Large Millimeter/ 
submillimeter Array in Chile, a facility still 
undergoing construction. — B. A. 

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^Q Astronews 

WonilCian WAiroc British scientists re-created natural sounds from Venus, Mars, and 
Veil Ubldl I VUKcb ot her worlds in a planetarium show that debuted April 4. 

! Still a ways to go 

Voyager 1 's Cosmic Ray Subsystem 
— experiment detected an increase in 
03 electrons and protons in 201 1, implying 
that the spacecraft is not as close to the 
border between the Sun's protective 
bubble and interstellar space as previously 
thought. William Webber of New Mexico 
State University in Las Cruces and 
colleagues analyze the roughly 25 percent 
signal increase in the March 29 Geophysical 
Research Letters. — L. K. 

Venusian oddity 

The Sun's coronal mass ejections and 
the aurorae in Earth's atmosphere are 
examples of magnetic reconnection. 
As oppositely directed magnetic field 
lines break and then combine, this 
"reconnection" leads to the conversion 
of magnetic energy into kinetic energy. 
Scientists report online April 5 in Science 
Express that the Venus Express spacecraft 
detected magnetic reconnection in Venus' 
atmosphere, even though the planet 
doesn't have an intrinsic magnetic field 
and thus the effect wasn't expected. — L K. 

25 years ago *****»% , 10 years ago 
in Astronomy (^ in Astronomy 

In the August 1987 issue, 
Joseph A. Lovece outlined a 
looming threat in "The 
Impending Crisis of Space 
Debris." He began with a col- 
lision between a "marble-sized 
piece of metal" and an orbiting 
telescope that destroys the 
instrument. "The space around 
our planet is polluted," Lovece 
wrote, and while that collision 
hadn't happened yet, it easily 
could. Of particular concern was 
the then-upcoming Hubble Space 
Telescope, a billion-dollar mission 
that faced a 1 percent chance of 
total destruction from space debris. ^ug 

Nowadays, of course, the problem has 
gotten worse and poses an even greater 
danger: The International Space Station must 
occasionally adjust its orbit to avoid poten- 
tial collisions. Space debris hasn't yet caused 
any catastrophic accidents, but, as Lovece 
noted, perhaps it's only a matter of time. 

The August 2002 issue featured a 
showcase of the latest and great- 
est space images in "Hubble's 
Grand New Vistas" by Astronomy 
Senior Editor Richard Talcott."You 
might think that after 1 2 years in 
orbit, the Hubble Space Telescope 
would be plumb out of surprises," 
he wrote. "Yet like a child enter- 
ing adolescence, Hubble stands 
on the threshold of an extraor- 
dinary new phase in its life." 

The reason was a servicing 
mission the previous March, 
the fourth out of an eventual 
five for the space telescope. 
Talcott described the newest 
instruments aboard Hubble while allowing 
its most recent breathtaking images to 
speak for themselves. "As the newly revital- 
ized space telescope prepares to enter its 
teenage years," Talcott wrote, "we can only 
guess at what surprises it holds in store." It 
continues to surprise us, even today. — B. A. 



What is the impact of finding 
galaxies that recycle 
star-forming material? 

by Karri Ferron 

Astronomers have long theorized that gal- 
axies consume gas that falls from inter- 
galactic space into their disks. There, the 
gas is gradually converted into stars, 
forming the spectacular galactic structures we 
observe. This fueling process is fundamental to a 
galaxy's growth, including that of the Milky Way. 
Yet for several decades, astronomers have found 
little direct evidence for this gas infall in the dis- 
tant universe and even have had trouble 
accounting for all the fuel needed to maintain 
our galaxy's current level of star formation. 

Within the past year, though, scientists have 
made great strides in understanding how galax- 
ies are fed. Researchers studying the gas clouds 
surrounding the Milky Way with the Hubble 
Space Telescope discovered a new reservoir of 
material falling onto our galaxy's disk. This mate- 
rial is plentiful enough to supply the missing fuel 

18 Astronomy -August 2012 

our galaxy needs to continue its slow growth. At 
the same time, another research group used 
Hubble to discover that normal star-forming gal- 
axies like the Milky Way are surrounded by mas- 
sive amounts of gaseous material that has been 
enriched with the debris produced during the 
explosive deaths of stars. Some of this material is 
so distant that it will never fall back into its host 
galaxy, but some of it is close enough that it 
could potentially reenter the galactic disk. 

My team's recent Keck observations have 
finally caught this reentry, or recycling, as it hap- 
pens, verifying our fundamental understanding 
of how galaxies grow. And with the next genera- 
tion of telescopes, we hope to measure the 
amount and enrichment of gas feeding galaxies 
as they evolve from 2 billion years after the Big 
Bang until today, showing just how important 
gas recycling is to the life cycle of galaxies. 




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Robot astrobiologist 

NASA's Mars Science Laboratory 
mission packs the most advanced 
suite of scientific instruments ever 
sent to another world, by Jim Bell 

f all goes as planned, earthlings once again will 
invade Mars sometime during the wee hours of 
August 6. Or, more accurately, a robotic emissary 
sent from Earth will invade the Red Planet in an 
attempt to solve some of the mysteries still held 
close by our planetary neighbor. The Mars Science 
Laboratory is the largest, most adept, and most 
expensive mission to explore Mars. In fact, its 
suite of scientific instruments and mechanical systems 
are the most advanced ever sent to another world. 
As the spacecraft descends through the planet's 
ruddy, dusty skies that day to a landing site in Gale Cra- 
ter, it will be loaded — quite literally — with curiosity. 
Indeed, "Curiosity" is the name of the rover more for- 
mally known as the Mars Science Laboratory. NASA 
designed this latest martian robot as a follow-on to the 
space agency's enormously successful twin Mars Explo- ' 
ration Rovers, Spirit and Opportunity, which landed in 
January 2004. But Curiosity is much bigger and far more 
capable — a car-sized mobile science lab intended to let 
mission scientists drive farther and make more-detailed 
measurements than any previous Mars rover. 

While NASA designed Spirit, Opportunity, and 
Sojourner (the rover on the 1997 Mars Pathfinder 
mission) primarily as robotic field geologists, mission 

Cu riosity explores the floor of Gale Crater in this artist's 
concept.The rover's mast rises some 7.2 feet (2.2 meters) above 
the martian surface. The ChemCam instrument for determining 
rock and soil composition rests at the mast's top while the 
two "eyes" of Mastcam sit just below it. nasa/jpl caitech 

20 Astronomy-August 2011 




Curiosity lifts off from Cape Canaveral, Florida, 
on November 26, 2011 . An Atlas V rocket 
launched the rover on an eight-month journey 

tO the Red Planet. NASA/ScottAndrews/Canon 


The Curiosity rover sits in a clean room at NASA's 
Jet Propulsion Laboratory in Pasadena, California, 
on April 4, 201 1 . The rover's mast stands tall while 
the robot arm is partially extended at left. 

planners built Curiosity as a robotic field 
astrobiologist. It is endowed with sophisti- 
cated instruments optimized to achieve the 
missions primary science goal: explore Mars 
as a potential habitat for life, past or present. 

Eyes on Mars 

Conducting this comprehensive search for 
signs of life won't be easy, but those of us 
controlling the rover will have a suite of a 
dozen science instruments at our disposal. 
Like the previous rovers, Curiosity has 
many sets of digital camera "eyes" to help it 
navigate, avoid hazards, and collect science 
data. Among the coolest of these is a pair of 
stereo-capable color science cameras called 
"Mastcam." Mounted 6.5 feet (2.0 meters) 
above the surface on the rover's mast, Mast- 
cam will capture full HD-quality photos 
and movies. The camera will be able to 
resolve geologic features as small as about 
14 inches across from a mile away (22 cen- 
timeters from a distance of one kilometer) 

Curiosity towers over its predecessors in the 
"Mars Yard" testing area at NASA's Jet Propulsion 
Laboratory in Pasadena, California. The flight 
spare for the first Mars rover, Sojourner (front), 
measures 26 inches (65 centimeters) long. A 
working test model of Spirit and Opportunity 
(back left) spans 5.2 feet (1 .6 meters) while 
Curiosity's test rover (right) is 10 feet (3m) long. 

and as small as 0.02 inch (0.5 millimeter) 
across in the area right around the rover, 
lust as exciting is the Mars Hand Lens 
Imager (MAHLI), a super-high -resolution 
color microscope mounted to the rover's 
robotic arm. MAHLI will resolve struc- 
tures 50 to 100 micrometers across — 
about the width of a typical human hair. 
At this scale, scientists will be able to see 
evidence of rock and mineral textures, the 
shapes of embedded grains, and distinctive 
colors that might provide clues about the 

area's mineralogy or the past action of 
water in the region. MAHLI also carries 
multiple light sources, so it can operate 
both day and night. 

Ken Edgett, the leader of the MAHLI 
team from Malin Space Science Systems, 
Inc., in San Diego, California, explains: 
"When you're out in the field and you want 
to get a quick idea what minerals are in a 
rock, you pick up the rock in one hand and 
hold your hand lens in the other. You look 
through the lens at the colors, the crystals, 
and the features that help you diagnose 
what minerals you see." 

Besides Mastcam and MAHLI, Curiosity 
has eight other onboard camera systems. 
These will help the science team drive the 
rover, position the robotic arm, point the 
chemical-analysis instruments, and take 
what should be a spectacular movie of the 
landing site and its surroundings while the 
spacecraft makes its descent to the surface. 

Using its other senses 

The rover carries more than just cameras, 
however. Curiosity is endowed with what 
some of us on the team lovingly refer to as 
"squiggly line" instruments because they 
will make observations that often need to 
be displayed as lines on a graph or chart. 
For example, the Alpha Particle X-ray Spec- 
trometer (APXS) will create squiggly line 
data that reveal the elemental chemistry of 
the samples it comes in contact with. The 
Chemistry & Mineralogy (CheMin) instru- 
ment also will use X-rays to identify chemi- 
cal elements as well as the mineral structure 
of its samples. And the Chemistry & Cam- 
era (ChemCam) instrument will use a laser 

Gale Crater, the target of NASA's Curiosity rover, lies just south of the martian equator. The probe 
will explore an area unlike any visited by the six previous landers and perhaps discover evidence for 
past or present life. This map shows all of Mars between 70° north and south latitudes, mola science Team 

22 Astronomy -August 2012 

beam to zap and vaporize rocks and soil up 
to 23 feet (7m) away and then analyze their 
elemental chemistry without needing to be 
in contact with the samples. 

Perhaps the most scientifically exciting 
of the squiggly line instruments, though, is 
the Sample Analysis at Mars (SAM) suite. 
These three miniaturized laboratory instru- 
ments will perform the most detailed 
search yet for organic molecules on Mars. 
If there is methane in the atmosphere, for 
example, SAM will be able to detect it. 
Some astronomers think methane formed 
geologically, but others suspect it to be a 
byproduct of microbial life beneath the 
martian surface. Even if there is no life on 
the surface of Mars today, SAM still could 
detect certain kinds of chemical-isotope 
signatures or organic-molecule remnants 
that might tell mission scientists that life 
existed on Mars long ago. 

A significant part of Curiosity's payload 
includes a complex system to collect and 
deliver samples to these other instruments. 
A drill, a brush, a scoop, and sieves work 
together to gather carefully selected rock 
and soil fragments and get them safely into 
the SAM and CheMin devices deep inside 
the rover's body. 

Curiosity also brings to Mars a weather 
station, a radiation monitor to assess condi- 
tions for future human exploration, and a 
neutron detector designed to search for 
evidence of water or ice in the martian sub- 
surface or trapped within minerals at the 
surface. Overall, it's an extraordinary set of 
capabilities for both remote and close-up 
science investigations of the materials the 
rover will encounter once on Mars. 


Curiosity may drive into this filled channel on the edge of Gale Crater's central mound. The color 
variations here mostly reflect differing amounts of loose dark sediment. NASA/jPL-caitech/umversity of Arizona 

A site for sore eyes 

To get the most out of these scientific 
observations, NASA needed to find the 
right landing spot for Curiosity. It wasn't 
easy. Mission scientists didn't want to 
end up at a scientifically boring site, 
the fate of the twin Viking landers in the 
mid-1970s. Fortunately, our team had far 
more information about Mars to work with 
than the Viking scientists had. During the 
past 15 years, an armada of four orbiters, 
two landers, and three rovers returned 
images of Mars and data about its compo- 
sition that have revolutionized scientists' 
understanding of this most Earth-like of 
planetary neighbors. 

About six years ago, NASA asked several 
hundred scientists who study Mars to pro- 
pose possible landing sites for Curiosity. 
The locations had to be not only where the 

Curiosity will land ^^^^^^ 

somewhere within the 

ellipse shown on the floor of the 96-mile-wide 

(1 54 kilometers) Gale Crater. After coming to rest in this 

relatively smooth, flat area, the rover will drive toward the large mound at 

the Crater's Center. NASA/JPL-Caltech/ESA/DLR/FU Berlin/MSSS 

rover could touch down safely, but also 
places where the mission could address its 
geologic, geochemical, atmospheric, and 
especially biologic science objectives. 

The scientists responded with dozens 
of spectacular suggestions. Potential sites 
included some near water-formed gullies, 
ancient streambeds, and river deltas, others 
where glaciers once flowed, and many in 
craters and valleys that boast mineralogi- 
cally interesting deposits of layered sedi- 
ments. Most of the proposed sites showed 
evidence for intriguing mineral signatures 
as well as exciting geologic landforms, help- 
ing to keep the squiggly line scientists just 
as interested as the photogeologists. 

But science wasn't the only deciding 
factor. NASA eliminated many sites because 
the presence of steep slopes, abundant large 
rocks, or loose sand posed too much dan- 
ger to prospects for a successful landing. 
And although spots near the large martian 
volcanoes might have been exhilarating, 
they didn't pass muster because the rover's 
landing parachutes wouldn't work properly 
in the thin air at those high elevations. 

Other possible sites fell victim to the 
frigid martian nights. The extreme cold 
places limits on how far from the equator 

Jim Bell is a planetary scientist, author, and 
professor in the School of Earth and Space 
Exploration at Arizona State University in Tempe. 
He is a member of the Curiosity rover's camera 
team, and since 2004 also has been the lead 
scientist for the Pancam color cameras on NASA's 
Spirit and Opportunity rovers. Bell's photo-rich 
space books include Postcards from Mars, 
Mars 3-D, and Moon 3-D. 23 

Curiosity could land. Although the rover 
will generate electricity through the radio- 
active decay of plutonium, like the Viking 
landers did, it has to devote a lot of power 
to run the heaters that keep the instruments 
and systems alive. The solar-panel technol- 
ogy employed by Sojourner, Spirit, and 
Opportunity simply can't supply enough 
energy to the far bigger Curiosity rover. 
Sometimes it seemed like there was a 
battle going on between the scientists, who 
wanted to land Curiosity at a geologically 
and mineralogically interesting site — 
which often meant dramatic, potentially 
dangerous terrain — and the engineers 
and managers, who sought a flat, boring 
site to maximize the chances of a safe 
landing. It was a friendly battle, however, 
because everyone knew the same basic 
truth: If the rover didn't survive the land- 
ing, we'd get zero science. 

All hail Gale Crater! 

After five years of often contentious meet- 
ings and debates, the scientists and engi- 
neers found a solution that should make 
both groups happy. Curiosity is set to land 
in Gale Crater. An ancient asteroid impact 
gouged out this deep, 96-mile- wide (154km) 
hole in the ground, which lies just 5° south 
of the martian equator. 

Even better, Gale Crater happens to have 
a 3-mile-high (5km) mountain of layered 
sedimentary rocks within it. The layered 
rocks in this central mound appear to span a 
period of Mars geologic time from the oldest 
epoch, when the planet was much warmer 
and wetter, to the middle epoch, when the 
planet began drying out, to modern-day 
deposits of dust that fall out of the atmo- 
sphere at the highest elevations. Gale's 
mound, nicknamed Mount Sharp, and its 
surroundings also show mineral signatures 

entry begins 

Altitude: about 

78 miles (125 kilometers) 

Velocity: about 13,200 mph 

(5,900 meters per second) 

Time since entry: 


Atmospheric deceleration 

Friction with the atmosphere slows 
spacecraft by more than 90 percent; 
the heat shield's temperature climbs to 
a maximum of about 3800° Fahrenheit 
(2100° Celsius). 

Parachute deploys 

Altitude: about 7 miles 
(1 1 kilometers) 
Velocity: about 900 mph 
(400 meters per second) 
Time since entry: about 
255 seconds 

Heat shield separates 

Altitude: about 5 miles 
(8 kilometers) 
Velocity: about 280 mph 
(125 meters per second) 
Time since entry: about 
279 seconds 

A complex series of maneuvers will deliver Curiosity from interplanetary space to the floor 
of Gale Crater. It should take about seven minutes from atmospheric entry to touchdown, 
although martian atmospheric conditions on landing day will affect the timing and altitude 
of the key events. The values quoted here are for a typical case. Astronomy-. Roen Keiiy; insets: NASA/jPL-caitech 

that indicate liquid water was once present. 
At the least, this water coursed through sur- 
face streams that carved giant canyons into 
the mound. But some scientists think the 
liquid ponded in an ancient lake almost the 
size of North Americas Lake Ontario. 

In addition to the spectacular scenery 
and diverse mineralogy, one other factor 

Curiosity probes a martian rock in this artist's concept. The robot arm holds two instruments: the 
Alpha Particle X-ray Spectrometer for analyzing composition and the Mars Hand Lens Imager for 
close-up photography of rock surfaces. NASA/jPL-caitech 

tipped the scales in favor of Gale Crater 
— part of its floor located approximately 
6 miles (10km) from the mound is rela- 
tively flat and smooth, and will be a safe 
place to land the rover. Once Curiosity 
arrives at this benign and somewhat inter- 
esting place on the crater floor, mission 
controllers will drive the rover to the much 
juicier geologic and mineral features 
exposed in the layered mound. 

The science team is already excited 
about visiting this site. Some of the scenery 
could be reminiscent of the canyons and 
mesas of the American desert southwest. 
The rover's traverse into and up the mound 
will be like taking a geologic field trip 
through martian history, including times 
when and places where the environment 
may have been habitable to life as we know 
it. Jim Green, director for the Planetary 
Science Division at NASA Headquarters 
in Washington, D.C., summarizes Gale's 
selection in this way: "The site offers a 

24 Astronomy -August 2012 







Radar collects data 

A radar system on the descent 
stage measures the spacecraft's 
exact velocity and altitude; 
meanwhile, the Mars Descent 
Imager photographs the surface 


Back shell separates 

Altitude: about 1 mile 
(1.6 kilometers) 
Velocity: about 1 80 mph 
(80 meters per second) 
Time since entry: 
about 350 seconds 

Rover separates 

Altitude: about 66 feet 
(20 meters) 

Velocity: about 1.7 mph 
(0.75 meter per second) 
Time since entry: 
about 390 seconds 



Altitude: feet 
Velocity: about 1 .7 mph 
(0.75 meter per second) 
Time since entry: 
about 403 seconds 


Pyrotechnic cutters on 
the rover sever the 
connecting cords, and 
the descent stage flies 
at least 492 feet 
(150 meters) away. 

visually dramatic landscape and also great 
potential for significant science findings." 

Floating out of the sky 

Engineers at NASA's Jet Propulsion Labora- 
tory in Pasadena, California, started con- 
structing Curiosity in mid-2007, although 
scientists and engineers from around the 
world provided many of the instruments 
and other components. Building a robot 
that needs to fly to and work on another 
planet is not an easy task, however, and the 
team ran into many unexpected technical 
hurdles and cost overruns. The project 
missed its first launch opportunity in 2009. 
The team ultimately finished assembling 
and testing the nearly $2.3-billion rover in 
time for its launch from Cape Canaveral in 
Florida on November 26, 201 1. 

It has taken a little more than eight 
months for the spacecraft to cruise from 
Earth to Mars, but the landing sequence 
from atmospheric entry to touchdown will 

last only about seven minutes. Curiosity will 
use a parachute, retro-rockets, and a "Sky 
Crane" to settle gently onto the martian sur- 
face. Engineers designed the unique landing 
system to deliver the craft to its target 
because it is too heavy to use air bags, as the 
previous rovers did. (See "Descent to the 
Red Planet" above for landing details.) 

The rover will arrive during the early 
morning hours of August 6 (late night 
August 5 in Pasadena), when it will be late 
afternoon at Gale Crater. If all goes well, 
Curiosity will explore the crater for at least 
one Mars year (nearly two Earth years), 
but given NASA's recent success in rover 
longevity, it could survive much longer. 

It is anyone's guess what Curiosity's 
remote-controlled senses will reveal. Does 
Gale Crater preserve evidence of past or 
present martian life among that spectacular 
pile of possibly water-lain sediments the 
rover will climb? Some on the team are 
skeptical while others are optimistic. All we 

really know is that scientists never will be 
able to answer the question "Are we alone?" 
unless they make the effort to search 
beyond the confines of our home planet. 
One of the best places astronomers have 
found to start that search is on the planet 
right next door, and robots like Curiosity 
provide a cost-effective way to begin. 

Many scientists believe that the search 
ultimately will prove too complex for 
robots, and that it will take human explorers 
on Mars — working in concert with robots 
— to reveal the planets biologic history. 
"Mars is firmly in our sights," says NASA 
Administrator Charles Bolden. "Curiosity 
not only will return a wealth of important 
science data, but it will serve as a precursor 
mission for human exploration to the Red 
Planet." It should be quite an adventure. »» 



To see an animation of Curiosity 
landing on and exploring Mars, visit 25 

Martian machines 

In 2004, NASA 

landed two robot 

geologists on 

Mars, hoping to 

get 90 days of 

workout of them. 

After eight years of 

exploration, Spirit 

and Opportunity 

have deepened 

our knowledge of 

the Red Planet. 

by Robert Burnham 

Nobody expected them to live long. 
When scientists and engineers 
designed the Mars Exploration 
Rovers, 90 days seemed enough to 
carry out the rovers' prime task — 
to discover and study rocks and 
soils holding clues to past water activity. This 
was in keeping with the theme of NASA's 
Mars exploration: "Follow the water." 

The rovers, named Spirit and Opportunity, 
were launched in June and July 2003, respec- 
tively, and arrived in January 2004. The first to 
land (on January 4) was Spirit, which targeted 
Gusev Crater — thought to hold lake bed sed- 
iments. Opportunity landed three weeks later 
at Meridiani Planum, a site that holds the 
planet's largest hematite deposit — about the 
size of Oklahoma. Hematite is an iron oxide 
that nearly always forms with water. 

Neither rover carried instruments to 
detect life directly, but water would be a key 
ingredient of any place that merited the label 
"habitable." To outfit the rovers, scientists 
gave them instruments that amounted to a 
robotic version of what every geologist car- 
ries into the field. 

Robert Burnham is the media relations manager 
for Arizona State University's Mars Space Flight 
Facility in Tempe. 

Spirit's and Opportunity's journeys and 
discoveries have surpassed scientists' expecta- 
tions. Both explored Mars for years, and one is 
still going; the rovers achieved their prime 
task by detecting many lines of evidence that 
water once existed on the Red Planet. 

Where to go on Mars? 

Meridiani Planum became a high-priority 
site thanks to the hematite discovery by the 
Thermal Emission Spectrometer on NASA's 
Mars Global Surveyor orbiter. Opportunity's 
Meridiani landing site, a couple of degrees 
south of the equator, also has light winds 
and flat ground. 

On the other side of Mars and 15° south 
of the equator, Gusev Crater promised water 
in a different way. The crater is about 100 
miles (160 kilometers) wide and has a mostly 
flat floor. An ancient river channel, Ma'adim 
Vallis, meanders down from the highlands to 
breach Gusev's south rim. Thus, the thinking 
went, Gusev was a slam-dunk for an ancient 
crater lake, and Spirit would probably land 
on lake bed sediments. 

The landing went smoothly. Spirit powered 
up, rolled off the descent stage, and looked 
around. It saw a smooth, flat landscape with 
small rocks nearby and enticing hills in the 
distance under a tawny sky. These were soon 

Spirit's second target, Columbia Hills, lies in the 
distance. Scientists estimated it would take the 
rover about 60 sols (martian days) to get there 
from its imaging position — putting Spirit past 
its nominal mission length of 90 sols. NASA/jPL/comeii 

named the Columbia Hills to honor the 
astronauts killed in 2003 when the space 
shuttle Columbia broke up. 

But three days after Spirit landed, the 
mission's principal investigator, Steven 
Squyres of Cornell University in Ithaca, New 
York, looked at the images and summed up 
his growing impression, "I don't think we've 
landed on bare lake bed deposits." 

Using the rover's instruments (see illus- 
tration on page 27) to study the soil and 
the closest large rock — named Adiron- 
dack — reinforced his conclusion. As far as 
cameras could see, dusty rocks made of 
volcanic basalt covered the plain. Lake sed- 
iments, if they existed, were probably bur- 
ied under lava flows. 

As mission control learned how to drive 
the rover through boulder fields, scientists' 
attention shifted to the other side of Mars. 

Opportunity touched down there 21 days 
after Spirit (January 25). When scientists 
turned on the rover's cameras, they were 
astonished and delighted to find it sitting in 
a shallow crater with bedrock directly ahead. 

Nearing twice the original mission's length, 
Spirit spots an odd-shaped rock, which team 
members nickname "Pot of Gold."The rock 
contains hematite, a mineral that usually forms 

With Water. NASA/JPL/Cornell 

Better still, the outcrop, nearly a foot high, 
appeared to have layers like sedimentary 
rock and was lighter in color than basalt. 
The rover's Miniature Thermal Emission 
Spectrometer (Mini-TES) mineral scouting 
instrument showed that the Meridiani land- 
scape is loaded with hematite. 

It amounted to an interplanetary hole in 
one: Opportunity came to rest directly 
upon the water- altered material it was sent 
to find. Primary science goal achieved, and 
the rover had barely set a wheel on Mars. 

Spirit: head for the Hills 

Over in Gusev, team Spirit was struggling. 
So, Squyres gave the rover's crew a new tar- 
get, a time line, and a change in operational 
style: Put science on the back burner, he 
said, and get Spirit to the Columbia Hills by 
sol 160, its 160th day on Mars. (The mar- 
tian day rhymes with "awl," and it runs 39 
minutes longer than Earth's day.) 

With a distance of 1.7 miles (2.7km) to 
cover, Spirit would have to make an average 
run of 66 yards (60 meters) every sol. 

Opportunity: seek sediments 

As Spirit chugged toward the Columbia 
Hills, Opportunity explored its first out- 
crop. Seen by the rover's Microscopic 
Imager and other instruments, the rocks 
showed textures that revealed its sand-sized 
sediments were laid down in moving water 
about a foot deep. The sediments proved 
rich in sulfur, chlorine, and bromine, which 
showed that water had repeatedly dried up 
and then returned. The biggest surprise 
was finding jarosite, an iron-bearing sulfate 
rock uncommon on Earth. 

Mini-TES spotted hematite all around 
the rover, and the cameras showed uncount- 
able small spherules a few millimeters in 
diameter littering the ground. The Moss- 
bauer Spectrometer, which determines the 
composition of iron-bearing minerals, 
clinched the connection: These "blueber- 
ries" (named for their size) are hematite- 
rich. They had formed within the outcrop 
rock as concretions by a chemical process 
similar to how an oyster turns grit into a 
pearl. And being tougher than the rock, the 
blueberries eroded more slowly, leaving 
them to cover the surface. 

Spirit, sol 1899 

Soft soil partially buries Spirit's wheel, leaving 
the rover unable to move. This same location 
is where the rover would send its last 
communication to Earth on March 22, 2010. 

28 Astronomy -August 2012 

▲ Atop the summit of Husband Hill, Spirit 
captures this panorama. As more than 1 50 
martian days pass, the rover inches upward 
along the north side of Husband Hill — some 
270 feet (82 meters) above the Gusev plain. 

With that, it was time (sol 58) for 
Opportunity to hit the road. About 2,300 
feet (700m) to the east lay a stadium-sized 
crater named Endurance, 430 feet (130m) 
wide and 70 feet (20m) deep. Inside, scien- 
tists hoped to see a much larger section of 
sediments than in the crater where Oppor- 
tunity landed. Opportunity reached the 
edge of Endurance on sol 95 and peered in. 

The rim and upper walls showed steep 
layers of sedimentary rocks; in the bottom 
were wind-sculpted dunes. Falling from the 
cliffs could easily destroy the rover, and the 
sand was no-go terrain. "We're going to have 
to be very careful here," thought Squyres. Yet 
in part of the rim, an area dubbed Karatepe, 
the crater's interior offered rocky pavement 
that sloped only about 20° — trafficable 
with careful driving. 

On sol 133, Opportunity took its first 
rolling step into Endurance. 

Spirit: odd rocks 

Spirit reached West Spur, an outlier of the 
Columbia Hills, on sol 159. Immediately, 
the rocks became interesting. 

Scientists gave the moniker Pot of Gold 
to the strangest rock any team geologist had 
seen. The size of a Softball, it has little nod- 
ules "like somebody took a potato and stuck 
toothpicks in it, then put jelly beans on the 
ends of the toothpicks," as Squyres describes 
it. And Spirit's analytical spectrometers 
showed Pot of Gold also holds hematite — a 
first for Spirit and boding well for finding 
water-altered rocks in the hills. 

After leaving Pot of Gold, the Spirit 
team began to deal with a mechanical prob- 
lem: The right front wheel started drawing 
about twice as much power as the others. 

Spirit's journey into the hills 

Bonneville Crater 

The martian rover Spirit drove a total 
of 4.8 miles (7.73 kilometers) over its 
six-Earth-year mission. Spirit last 
communicated with scientists in March 
2010, before the martian winter set in. 

Landing site 

500 yards 

Soli 64 

c ol 620-622 


I I 


Opportunity's crater tour 

.' / 

Endurance Crater 
" Sol 330 
Sol 339 

Opportunity has covered some 16 
miles more martian ground than its 
twin, Spirit, and it's still exploring 
the Red Planet after 21 .36 miles 

(34.38 kilometers). NASA/JPL/Univ. of Arizona 

Sol 11 62 

Santa Maria 

4,000 meters 

4,000 yards 

Sol 2820 

' Cape York 


Cape York 
Botany Bay 

Solander Pot 


— Cape Tribulation 

Engineers decided to alternate driving the 
rover facing forward and in reverse in 
hopes to even out the wear. 

By this point, Spirit had lasted twice its 
nominal mission length. Moreover, the solar 
panels had collected dust, preventing them 
from delivering as much power. And finally, 
martian winter was approaching, with 
nights getting colder and the Sun daily lower 
in the north. The rover had power for only 
an hour or so each day, so engineers drove 
Spirit slowly into Columbia Hills, keeping it 
on slopes leaning north toward the Sun. 

Finally, on sol 581, Spirit reached Hus- 
band Hill's summit. To the southeast was 
the Inner Basin, a shallow depression nes- 
tled between the hills. 

Spirit watched as dust devils whirled by 
on the plains, and a gust of wind must have 
passed over the rover because one morning 
it woke up with its panels nearly as clean as 
the day it landed. 

Spirit would descend into the Inner Basin 
and head for an enigmatic feature dubbed 
Home Plate. What it was no one knew 
(maybe lake bed deposits?), but it looked 
different from everything else in the hills. 

Opportunity: deeper history 

In Meridiani, mission control placed Oppor- 
tunity on the north-facing inner slope of 
Endurance at Karatepe. There, the rover 
used its Rock Abrasion Tool (RAT) to grind 
into exposed rocks and then deployed its 
spectrometers. The results showed that 
water had been episodically present, with 
repeated floods followed by dry periods. 

The rovers last stop in Endurance was 
Burns Cliff. Amazingly, Opportunity was 
able to drive partway up the bottom of the 
cliff slope. Describing the rocks, the science 
team reported that the Burns formation is 
made of sedimentary rocks that a wind- 
swept, arid surface environment created. 
Water, they said, rose occasionally to the 

Cape Bryson 


Cape Dromedary 

Point Hicks 

The second crater Opportunity visits is 
Endurance. The rover spends some 200 
martian days exploring the floor and 

exposed WallS. NASA/JPUCornell 

surface, and sulfate-rich sand grains were 
reworked by the wind to form dunes and 
sand sheets. The multiple floodings by 
groundwater changed the rock and formed 
the hematite-rich blueberries. 

On sol 315, Opportunity drove out of 
Endurance onto the Meridiani plains again. 
About 4 miles (6km) south lay a crater 
named Victoria, six times larger than 
Endurance and more than three times 
deeper. Scientists hoped to find older layers 
than those in Endurance — but it would be 
a long drive, some 18 to 20 months. Oppor- 
tunity started south on sol 352. 

Spirit: rounding Home Plate 

Meanwhile, Spirit descended from the top 
of Husband Hill into the Inner Basin. On 
sol 697, it arrived at outcrops named 
Comanche and Comanche Spur. Spirit's 
instruments studied them, but Comanche's 
big secret — that it is full of carbonate min- 
erals left by water — didn't emerge until 
more than four Earth years later. 

"Mini-TES got dusted months before 
Spirit reached Comanche, and at the time 

The upper and lower portions of the rock 
outcrop "El Capitan"have different textures, so 
Opportunity uses its Rock Abrasion Tool to 
sample the soil at both locations. The outcrop is 
just 4 inches (10 centimeters) tall, nasa/jpl 

Hematite "blueberries" scatter across the 
ground in a rock outcrop near Opportunity's 
landing site, providing the rover with immediate 
evidence of past water activity. NASA/jPL/comeii 

we didn't have a good way to correct for it," 
says Steve Ruff, lead Mini-TES scientist at 
Arizona State University in Tempe. "We 
knew there was something weird about the 
outcrop's spectrum but couldn't say what." 

Developing a calibration to remove the 
effects of the dust took several years, but it 
did the trick. "Small amounts of carbonates 
have been detected on Mars before," Ruff 
explains. But with Comanche, "the rocks are 
about 25 percent carbonate by weight — by 
far the highest abundance seen on Mars." 

After Comanche, Spirit drove steadily 
downhill toward Home Plate, a low plateau 
about 7 feet (2m) high and 260 feet (80m) 
across. It arrived on sol 746. 

On sol 754, Spirit imaged a golf-ball- 
sized rock sitting in a shallow little crater 
on the edge of Home Plate. The rock is 
what geologists call a volcanic bomb, and 
the mini-crater is the "splat mark" where it 
landed. This supported the idea that Home 
Plate might be a hot spring or steam vent. 
Yellowstone National Park in Wyoming has 
many such features. 

As Spirit headed away from Home Plate, 
the soil grew softer and harder to drive on. 
On sol 779, the long-balky wheel stopped 
turning altogether. Engineers decided to 
drive Spirit thereafter in reverse, letting the 
stuck wheel drag. 

An iron meteorite about the size of a basketball 
sits on the ground near Opportunity's heat 
shield. Dubbed "Heat Shield Rock," it is the first 
meteorite to be identified on another planet. 

But the season was advancing. For its 
second winter on Mars, engineers drove the 
rover back toward Home Plate and tipped it 
northward at a site called Low Ridge. 

Opportunity: rolling to Victoria 

Opportunity's drive south to Victoria Crater 
would last more than 600 days. The trip was 
mostly uneventful. Opportunity motored 
onward, although daily driving periods grew 
shorter as its solar power dwindled. 

Gradually, bits of Victoria's rim poked 
above the horizon, and Opportunity 
reached the edge of the 0.5-mile- wide 
(0.8km) crater on sol 953. Its cameras saw 
rugged walls with layers of exposed rock 
nearly 50 feet (15m) high and a floor blan- 
keted with dunes. The rim itself was deeply 
scalloped into bays and promontories. 

The top part of the stack of layers 
exposed in the walls appeared to be rubble 
thrown outward by the impact that dug the 
crater. "We see an abrupt transition between 
the jumbled- up material and intact layers 
below it that are still in place from before 
the impact," says Squyres. "Every promon- 
tory has the kinds of layering expected for 
ancient wind-blown sand deposits." The 
layers are made of sulfate-rich sandstone 
similar to the bedrock Opportunity had 
been seeing since landing on Mars. 31 

Opportunity, sol 330 






The rovers' upgraded software allows them to drive around obstacles that they encounter, like this 
patch of large rocks in Opportunity's path. NASA/jPL-caitech/comeii university 

But just as Opportunity was about to 
enter the crater at a location called Duck 
Bay, a global dust storm cut sunlight to only 
1 percent of its normal level. All of Oppor- 
tunity's activities (Spirits too) came to a 
halt until skies cleared about 50 days later. 

Spirit: martian Yellowstone? 

Spirit stayed parked from sol 805 to 1037. 
More hot-spring evidence surfaced when the 
rover drove again. Heading northward up 
the east side of Home Plate, the stuck wheel 
dragged a trench. "The trench looked bright 
white," Ruff recalls, "but we thought initially 
it was just more sulfate minerals." 

He then got curious: "We aimed Mini- 
TES at the trench and saw a clear silica 
spectrum. The rover's Alpha Particle X-Ray 
Spectrometer told us the white soil was 
more than 90 percent silica. That's a record 
high for silica on Mars." 

Making such pure silica requires a lot of 
water, says Ruff. "On Earth, the only way to 
have this kind of silica enrichment is by hot 
water reacting with rocks" — like at Yellow- 
stone National Park's hot springs. 

The find linked the silica with Home 
Plate, which the rover team already knew to 
be a volcanic feature. "We saw where rocks 

were thrown into the air and landed to 
make small indentations in the soft, wet ash 
sediment around the vent," says Ruff. 

Once alerted about what to look for, the 
scientists discovered more silica in many 
places nearby. As Ruff says, "It's not just the 
soil in a trench in one place. It's a broader 
story of outcrops that extend 50 meters 
[160 feet] away from Home Plate. This 
wasn't a small-scale, modest phenomenon." 

The same dust storm that idled Oppor- 
tunity also put Spirit on hold. After skies 
cleared, on sol 1309, scientists drove the 
rover up onto Home Plate, where it slowly 
toured the perimeter. By the time it reached 
the plateau's northern edge on sol 1410, 
controllers had to prepare Spirit for its third 
winter. It found a location slightly off Home 
Plate's edge with good northern exposure. 

Opportunity: Victoria's secrets 

On sol 1292, Opportunity drove into Victo- 
ria Crater. "We see evidence from orbit for 
clay minerals under the layered sulfate mate- 
rials," says Raymond Arvidson of Washing- 
ton University in St. Louis, Missouri. "These 
indicate less acidic conditions. The big pic- 
ture appears to be a change from a more 
open hydrological system with rainfall to 

Shortly after leaving Endurance Crater, 

Opportunity pays a call on some terrestrial 
debris: the wreckage of its heat shield discarded 
on landing. Engineers want to see how the heat 
shield withstood the fiery entry into the martian 
atmosphere. NASA/jPL/comeii 

more arid conditions with groundwater 
rising to the surface and evaporating, leav- 
ing sulfate salts behind." 

Opportunity examined a bright band of 
rocks around the inner wall of the crater. 
Inspection suggested that Victoria was at 
the top of an underground water table. 

Experiments with simulated Mars con- 
ditions and computer modeling helped 
researchers assess whether the long-ago 
environment at Meridiani would have been 
hospitable to microbes. 

"Life at the martian surface would have 
been very challenging for the last 4 billion 
years," says Andrew Knoll from Harvard 
University in Cambridge, Massachusetts. 
Conditions may have been more hospitable 
earlier. "The best hopes for a story of life on 
Mars are at environments we haven't stud- 
ied yet — older ones, subsurface ones." 

Opportunity's data suggested that the 
wind deposited the Victoria sediments, and 

Opportunity drives along a sand ripple and 
keeps its solar panels tilted northward to 
maximize the limited sunshine. NASA/jPL-caitech 

32 Astronomy -August 2012 

Mars in the raw 

You can keep up with Opportunity's trek 
by seeing the raw images it sends back 
every few days. Go to http://marsrovers. 
and pick which camera you wish to see. 
All images are in JPEG format. 

The views from the Hazard Cameras 
(Hazcams) look distorted because they're 
taken through fisheye lenses. File names 
are complicated, but there's a link on the 
page that tells you how to decode them. 

Spirit has an identical raw-image page, 
where you'll see that its last photos (out 
of 1 28,224 in all) are from sol 2208 (March 
21, 2010): 

Finally, to follow the mission sol by sol, 
check out: 

groundwater altered them. "The patterns 
broadly resemble what we saw at the 
smaller craters explored earlier," says sci- 
ence team member Scott McLennan of 
Stony Brook University in New York. "By 
looking deeper into the layering, we are 
looking further back in time." 

While exploring Victoria, a spike in 
electric power drawn by the rover's left 
front wheel resembled one seen on Spirit 
before its right front wheel failed. Opportu- 
nity's six wheels still worked, but the team 
heeded the warning. If the rover lost the 
use of a wheel while inside Victoria, it 
would probably be stuck in the crater for- 
ever. Once on flat ground, however, five 
wheels would suffice to keep it going. 

Spirit: winter's icy hand 

Spirits third winter lasted from sol 1410 to 
sol 1760. With the rover's solar panels dusty 
and the Sun low, Spirit generated enough 
power to keep alive, but its science activities 
were rationed. When spring came, Spirit 
was no longer able to climb up on Home 
Plate. So engineers turned the rover west. 

On sol 1870, Spirit reached a site named 
Troy and positioned itself to go up a low 
ramp on the south side of Home Plate. But 
on the next day's drive, the wheels on one 
side of the rover sank into the soil of a 
small crater named Scamander, and the 
rover stopped. Drive attempts on following 
days merely embedded Spirit's wheels ever 
more deeply in the soft ground. 

Spirit remains at Scamander today. 

Opportunity celebrates its eight-Earth-year anniversary atop Greeley Haven, an outcrop at 
Endeavour Crater's rim. The rover has far surpassed the original 90-martian-day mission length and 
continues to excite mission scientists with its discoveries. NASA/jPL-caitech/comeii/Arizona state univ. 

Mission engineers spent 10 months try- 
ing to free the rover, but they labored in vain. 
On sol 2156, NASA changed Spirit's mission: 
Scientists would track its radio signals to 
detect tiny wobbles in Mars' rotation, a task 
impossible with a mobile rover. The data 
would yield insight about the planet's core. 

On sol 2210 (March 22, 2010), Spirit 
reported that it was operating normally 
under its master control program, and all 
systems were "green." But its next downlink, 
scheduled for eight days later, never came. 

Engineers anticipated that as sunlight 
and power strengthened in spring 2010, the 
rover would awaken and re-establish com- 
munication with Earth. 

But Spirit never woke up. 

Opportunity: the big road trip 

On sol 1622, after a year spent exploring 
Victoria from the rim and another year 
inside, Opportunity was back out on the 
plains and on its way to Endeavour Crater, 
approximately 7 miles (12km) to the south- 
east. Endeavour is huge — 14 miles (22km) 
wide — and rising above the Meridiani 
plains are old rim segments, which are the 
crater's main attraction for scientists. As a 
bonus, clay minerals, which form exclu- 
sively under wet conditions, were spotted 
from orbit in parts of Endeavour's rim. 

The great trek began on sol 1682 (Octo- 
ber 17, 2008). Around sol 2260, Opportu- 
nity turned southeast on a more direct 
route to Endeavour. As it drove, the rover 
studied eroded craters, including Santa 
Maria (295 feet [90m] wide), and discov- 
ered several meteorites. 

Finally, on August 9, 201 1, which was sol 
2680 of the rover's original 90-sol mission, 

Opportunity arrived at Cape York, Endeav- 
our's nearest rim segment. Since it landed 
back in January 2004, Opportunity had 
driven 20.81 miles (33.49km). 

The rim rocks at Endeavour are impact 
deposits from the Noachian period some 4 
billion years ago, and are older and com- 
pletely different in type from the flat sedi- 
ments that Opportunity had driven on for 
the previous eight years. In a real sense, a 
new rover mission began at Endeavour. 

By any measure, Opportunity is now a 
senior citizen. The radioactive cobalt-57 
source in its Mossbauer Spectrometer has 
decayed in strength to the point where 
measurements that took an hour when the 
rover landed now take a month. The RAT 
still has some grinding left, and the cam- 
eras all work fine. But the instrument arm 
has a frozen joint, the wheel drivers show 
wear, and the solar panels are dusty. Mini- 
TES, which would be invaluable among the 
varied rim rocks at Endeavour, stopped 
working on the trip from Victoria. 

So what's Opportunity's future? On sol 
2947 (May 8, 2012), it drove down from 
Greeley Haven, its winter parking spot, to 
study a patch of nearby dust. Opportunity 
will drive south along the inner slope of 
Cape York, heading for Cape Tribulation, 
the next large rim segment. Among other 
things, it'll hunt for those clay minerals 
glimpsed from orbit. 

But whether Opportunity's future is long 
or short, it will continue to take us along on 
its incredible journey, across a beautiful 
and desolate planet. <» 


Visit to learn 
about the meteorites the rovers found. 33 

Landing humans on the Red Planet will be difficult and dangerous — 

but it can be done, by Richard Talcott; illustrations by Roen Kelly 

on the Moon's dusty gray surface July 
20, 1 969, It was the heart-stopping 
culmination of a decadelong 

rush to send people to our 
. next-door neighbor. In 
the more than 40 
years since, 
the human 

exploration of the solar system has 
proceeded at a decidedly slower pace. 

Mars has all the qualities a space- 
faring nation or nations could want 
for the next destination. The Red 
Planet lies relatively close to Earth, 
so the journey can be completed in 
a reasonable period, .and it possesses 
a fairly benign environment. 

The Mars Design Reference Archi- 
tecture 5.0 described here is NASA's 
most recent outline for suoh a mission. 
Although the plan may change before 
the space agency implements it, the 
overall framework likely will look simi- 
lar whether the United States, some 
other country, or an international 
effort ultimately achieves the goal. 

Richard Talcott is an Astronomy senior 
editor and author ofTeach Yourself Visually 
Astronomy (Wiley Publishing, 2008). 


Mission designers will use Mars' atmosphere 
to slow the massive cargo spacecraft enough 
for the planet's gravity to capture them into 
orbit. Rocket firings will then lower vehicles 
to the surface. Current plans call for aerocap- 
ture of the crewed 
vehicle as well. 


magazine w 

Landing strategy 


The so-called entry, descent, 

and landing phase of the 


mission carries high risk. Mis- 
sion planners will have to 
devise a way to bring a 40- to 
60-ton spacecraft from 

hypersonic orbital speed to a 
soft landing on the surface in 
less than 1 minutes. 

Ascent vehicle and 

exploration equipment 

touch down 

on the surface « 

Habitat/lander, ascent vehicle, 
and more arrive at Mars 
and enter orbit 

Surface operations 

When astronauts arrive, their 
equipment for exploring Mars will 
be waiting for them along with a 
fully fueled vehicle to return them 
to orbit. Rovers will carry the crew 
hundreds of miles from their safe 
landing site to study scientifically 
exciting regions. 

Power Source: The Mars habitat 
will operate on nuclear power, the 
only source capable of delivering a 
constant supply of abundant energy. 

Oxygen generation: The Mars 

base will produce oxygen from the 
planet's atmosphere to use as fuel 
for the ascent vehicle and as backup 
for life support. 


The Sky this Month 

Martin Ratcliffe andAlister Ling describe the solar system's 
changing landscape as it appears in Earth's sky. 

August 2012 

Neptune shines at its brightest 

Neptune's atmosphere glows blue-gray through amateur telescopes, but 
don't expect to see details like Voyager 2 recorded in 1989. nasa/jpl 

Neptune glows at magnitude 7.8 throughout August. It lies opposite the 
Sun on the 24th, when it appears 1° east of 38 Aquarii. Astronomy. R 0en Keii v 

Bright planets 
occupy both eve- 
ning and morning 
skies this month 
while one of their 
fainter siblings, distant Nep- 
tune, reaches opposition and 
peak visibility. As darkness falls, 
Mars, Saturn, and Virgo's prom- 
inent star Spica form an elegant, 
color-contrasting trio. A cres- 
cent Moon adds to their beauty 
when it passes by on the 21st. 
A more brilliant spectacle 
adorns August mornings. Both 
Mercury and Venus lie farthest 
from the Sun and highest in the 
sky at midmonth. Jupiter com- 
pletes the scene from its perch 
above the two inner planets. 
Our planetary tour begins 
August 1 when three lst- 
magnitude objects hang low 
in the southwest as the sky 
darkens. Saturn and Mars 
shine at magnitudes 0.8 and 1.1, 
respectively, and stand 8° apart. 
With each passing day, the two 
approach each other. Between 
August 7 and 20, they lie within 
a 5° circle that also includes 
magnitude 1.0 Spica. On the 
7th, the three form a neat equi- 
lateral triangle 4° on a side. 

Sunlight reflecting off Sat- 
urn's cloud tops has a golden 
glow while Mars' ruddy deserts 
cast an orange hue. They con- 
trast with the hot sun Spica, a 
blue giant star that generates its 
own light from a surface seeth- 
ing at 22,000 kelvins — nearly 
four times hotter than the Sun. 

If you could take a time- 
lapse movie of these objects 


Neptune comes 
to opposition 



Meteor watch 



Rising Moon 



When to view 
the planets 



A colorful 



Comet search 







A morning line <tt>zfi! 
of planets 

Visible to the naked eye 
Visible with binoculars 
Visible with a telescope 

during August, you would see 
Mars and Saturn sliding in 
front of Virgo's stars. Mars, 
the closer of the two planets to 
the Sun, moves faster than dis- 
tant Saturn. (The background 
stars remain stationary relative 
to each other.) 

Consequently, Mars soon 
passes between Saturn and 
Spica. On August 13 and 14, 
the three form a nearly straight 
line. A week later, on August 21, 
the trio makes a second equilat- 
eral triangle (now with 5°-long 
sides) punctuated by a gorgeous 
crescent Moon hanging 4° 
below Mars. In the deepening 
twilight, the objects create a 
perfect scene for wide-angle 
photography. For the best shots, 
include some photogenic fore- 
ground trees or buildings. 

36 Astronomy -August 2012 

By August 31, Mars trails 
10° behind Saturn and Spica. 
The trio sets within two hours 
of the Sun. 

When viewed through a 
telescope, Mars doesn't offer 
much. Its tiny disk measures 
5" across, leaving everything to 
the imagination as it shimmers 
in the eyepiece. But the surface 
should come into sharp focus 
the night of August 5/6, the 
date NASA's Curiosity rover is 
set to touch down on the Red 
Planet. For more information 
about the car-sized rover's mis- 
sion, see "Will Curiosity find 
life on Mars?" on page 20. 

Although Saturn lies six 
times farther from Earth than 
Mars, the ringed planet looks 
far better through a telescope. 
That's partly because its physi- 
cal diameter is 18 times bigger 
than Mars', so its apparent 
diameter is three times larger 
(16"). But even more important, 

Martin Ratcliffe provides profes- 
sional planetarium development 
for Sky-Skan, Inc., from his home 
in Wichita, Kansas. Meteorologist 
Alister Ling works for Environment 
Canada in Edmonton, Alberta. 

Risinq Moon 

Saturn has a beautiful ring sys- 
tem that spans 37". The rings 
tilt 14° to our line of sight in 
mid- August, offering us a fine 
view of their northern face. 

With Saturn now hanging 
low in the evening sky, most of 
its moons will be difficult to 
spot. But its biggest and bright- 
est satellite remains on view 
all month. Titan glows at 9th 
magnitude and takes 16 days to 
orbit Saturn. The moon appears 
closest to the planet when it 
passes either north or south 
of the globe. Look for Titan 
north of Saturn August 16 and 
south of it August 8 and 24. 

Neptune reaches opposition 
August 24, when it lies opposite 
the Sun in our sky and remains 
visible all night. It also appears 
brightest at opposition (mag- 
nitude 7.8), but it changes so 
slowly that you won't notice any 
difference during the month. 
And it's still dim enough that 
you'll need binoculars or a tele- 
scope to spot the distant world. 

Neptune lies among the stars 
of Aquarius, in the same binocu- 
lar field as 5th-magnitude 38 
Aquarii. You'll find the planet 
1.7° east of the star August 1 and 
— Continued on page 42 

Meteor watch 

Polaris* ' 




.*> • PERSEUS 

# Pleiades 

August 12, 1 A.M. 
Looking northeast 

The Perseid meteor shower peaks the night of August 11/12, when 
viewers can expect to see up to 80 meteors per hour. Astronomy. Roen Keiiy 

Perseids set to put on a great show 

If weeknight observing leaves you tired and cranky, here's some 
good news: One of this month's premier events occurs Saturday 
night, August 11/12, when the Perseid meteor shower reaches its 
annual peak. Start observing around midnight local daylight time. 
Although a waning crescent Moon rises shortly after 1 a.m., it 
won't have much impact because the shower consistently pro- 
duces lots of bright, fast-moving meteors. 

Observers under clear dark skies likely will see 60 to 80 meteors 
per hour streaking across a spectacular predawn sky that includes 
the bright planets Venus and Jupiter. Perseid meteors are tiny 
chunks of rock and dust from Comet 1 09P/Swift-Tuttle. When 
Earth plows through this debris stream each August, our planet's 
atmosphere incinerates these particles. 

Youthful rays in a sea of ancient lava 

You can double your chances to catch some lunar rays this month. 
Two Full Moons grace August's sky, on the 1st and 31st. Although 
the second Full Moon in a calendar month has the popular nickname 
"Blue Moon," the completely lit orb on the 31st will be anything but 
blue. Full Moons in summer lie low in the southern sky for observers 
at midnorthem latitudes, so they tend to appear more yellow than 
their wintertime white. Throw in some haze from high humidity or 
smoke from forest fires, and the Moon may look orange or even pink. 

Many lunar observers consider the Full Moon's most impressive 
feature to be the craterTycho and its magnificent ray system. The rays 
are finely crushed particles that splashed out during the impact that 
formed Tycho. Your eye naturally follows the longest ray to the north- 
east, where it splits Mare Serenitatis (the Sea of Serenity) nearly in half. 

The ray intersects Serenity's southern shore at the bright circular 
crater Menelaus.This 17-mile-wide impact structure has sharp edges 
and a light-hued debris apron that is characteristic of relative youth. 
Next, follow Tycho's ray northward into Mare Serenitatis, where it 
crosses the 10-mile-wide impact crater Bessel. 

Now look carefully at the sea of ancient lava around these craters. 
Planetary scientists estimate that the darker shade is 3.8 billion years 

Menelaus and Bessel stand out near the southern shore of Mare 
Serenitatis, particularly around Full Moon, when a bright ray from 

distant TychO pierces the pair. Consolidated Lunar /Utos/UA/LPL 

old. The lighter layer just to the north clocks in closer to 3 billion 
years. Can you see more white flecks — the telltale signs of tiny 
impact craters — in the darker, older zone? 

Astronomers have learned that darkness usually equates with age 
on the Moon. Rays and debris aprons darken with time as energetic 
particles in the solar wind constantly blast the lunar surface. 37 

The all-sky map shows 
how the sky looks at: 

1 1 p.m. August 1 
10 p.m. August 15 
9 p.m. August 31 

Planets are shown 
at midmonth 




Sirius ■-...•• Open cluster 

U7 Globular cluster 

10 l-l 
#20 ' ' diffuse nebula 

• 3.0 -<$- planetary nebula 

• 4.0 

• 5.0 ° Galaxy 



' /«P 

S *Gi Tr 

A *W S 



a. . . 

i fc» 

August 2012 

Note: Moon phases in the calendar vary in 
size due to the distance from Earth and are 
shown at Oh Universal Time. 

Quick fact: The Full Moon on 

August 31 is the second of the month, 

making it a "Blue Moon."This is the first 

Blue Moon for the Americas since December 

2009; it won't happen again until July 201 5. 


magazine W 






























































Calendar of events 

1 ■• Full Moon occurs at 
1 1 :27 p.m. EDT 

3 Jupiter passes 5° north of Aldebaran, 
1 A.M. EDT 

The Moon passes 6° north of 
Neptune, 6 p.m. EDT 

6 The Moon passes 5° north of Uranus, 
1 p.m. EDT 

7 Mercury is stationary, 1 p.m. EDT 

9 fc Last Quarter Moon occurs at 
W 2:55 p.m. EDT 

Asteroid Pallas is stationary, 
4 p.m. EDT 

10 The Moon is at apogee (251, 110 
miles from Earth), 6:51 a.m. EDT 

1 1 The Moon passes 0.1 ° south of 
Jupiter, 5 p.m. EDT 

Special observing date 

12 The Perseid meteor shower peaks 
before dawn, when observers 
with clear skies can expect to see 
an average of 60 to 80 meteors 
per hour. 

12 Mars passes 1 .9° north of Spica, 
8 p.m. EDT 

1 3 The Moon passes 0.6° north of Venus, 
4 P.M. EDT 

15 Venus is at greatest western 
elongation (46°), 5 a.m. EDT 

16 The Moon passes 4° south of 
Mercury, 1 a.m. EDT 

Mercury is at greatest western 
elongation (19°), 8 a.m. EDT 

17 Mars passes 3° south of Saturn, 

5 A.M. EDT 

New Moon occurs at 
11 :54 a.m. EDT 

21 Asteroid Hygiea is at opposition, 
4 P.M. EDT 

The Moon passes 1 .0° south of Spica, 

6 P.M. EDT 

The Moon passes 5° south of Saturn, 
1 1 p.m. EDT 

22 The Moon passes 2° south of Mars, 
4 A.M. EDT 

23 The Moon is at perigee (229,739 
miles from Earth), 3:28 p.m. EDT 

24 Neptune is at opposition, 9 a.m. EDT 

A First Quarter Moon occurs at 
™ 9:54 a.m. EDT 

26 The Moon passes 0.7° south of Pluto, 
10 p.m. EDT 

31 The Moon passes 6° north of 
Neptune, 1 a.m. EDT 

Full Moon occurs at 
9:58 a.m. EDT 

See tonight's sky in 's 



Planets in August 2012 





Angular size 


Distance (AU) from Earth 

Distance (AU) from Sun 

Right ascension (2000.0) 

Declination (2000.0) 

August 15 






August 15 

August 15 

August 15 






















1 1 1 njl am'c niAAnC Dots display positions of Galilean satellites at 4 a.m. EDT on the date shown 




South is at the top to match the view through a telescope. 






28 O 

I Astronomy- August 2012 

This map unfolds the entire night sky from sunset (at right) until sunrise (at left). 

Arrows and colored dots show motions and locations of solar system objects during the month. 


August 15 

August 15 

August 15 



August 15 

August 15 









-19*31 ' 



Greatest western elongation 
is August 15 

The planets in their orbits 


Arrows and dots show 

planets' positions 

during August. 



Opposition is August 24 

Continued from page 37 

When to view the planets 


Mars (southwest) 
Saturn (southwest) 
Neptune (east) 


Uranus (east) Mercury (east) 
Neptune (southeast) Venus (east) 
Jupiter (east) 
Uranus (southwest) 
Neptune (southwest) 

about half that distance by 
month's end. This region doesn't 
have many bright stars, so use 
the finder chart on page 36 to 
home in on the remote planet. 

When you aim a telescope 
at Neptune, boost the magni- 
fication to see the planet's 
2.4"-diameter disk. Note its dis- 
tinct blue-gray hue, a color gen- 
erated by the abundant methane 
in Neptune's atmosphere. This 
gas preferentially absorbs the 
red part of the solar spectrum 
and feebly reflects what's left. 

Scan farther east in the late- 
summer sky to pick up Uranus. 

Comet search 

It lies in the northwestern cor- 
ner of Cetus the Whale, just 
over the border from Pisces 
the Fish. These constellations 
rise in the east around the time 
Mars and Saturn set in the west. 
Like Neptune, Uranus lies in a 
region devoid of bright stars. 
To find the right area, scan 
with binoculars a bit more than 
one-third of the way from 3rd- 
magnitude Algenib, the star at 
the southeastern corner of the 
Great Square of Pegasus, to 
2nd-magnitude Beta (p) Ceti. 

Uranus and its stellar neigh- 
bor, 44 Piscium, both glow 
at magnitude 5.8. Through 

Spy a comet among Bootes' flock of stars 

Whether you're breaking in a new telescope or reacquainting your- 
self with a dark sky at a summer star party, get ready to test your 
comet-hunting skills. This month's brightest visitor from the solar 
system's depths likely will be C/201 1 F1 (LINEAR), which should 
glow feebly at 1 1th magnitude. 

The comet floats above brilliant Arcturus in the western sky as 
night sets in. Wait until the Moon is out of the evening sky during 
the second and third weeks of August to hunt for LINEAR. Use the 
finder chart at right to zero in on the comet's position. Rho (p) and 
Sigma (o) Bodtis, the pair of 4th-magnitude stars at the map's top 
left, lie 12° north-northeast of Arcturus. 

Using at least a 6-inch telescope, bump up the power past lOOx 
to darken the background sky and make the comet's small diffuse 
patch a bit bigger. Gently tapping the scope's tube can help you pick 
up the ghostly glow because it brings your motion-sensitive averted 
vision into use. View the star chart with your non-observing eye to 
protect your dark adaption as much as possible. 

If you're still having trouble, ask an observer with a larger light 
bucket for a quick look. Sometimes after you see a faint fuzzy in a 
big scope, you can detect it in a smaller one — another benefit of 
attending a star party. 

Meanwhile, the morning sky offers a comet that might reach 10th 
magnitude. If we're lucky, Comet 185P/Petriew will experience an 
outburst similar to the one that allowed amateur astronomer Vance 
Petriew to discover it accidentally 1 1 years ago at the Saskatchewan 
Summer Star Party. This comet lies near the Crab Nebula (M1 ) in 

• Arcturus 



Mars* •Saturn , 
Moon ^JpSpica 

• I 1 

• 10° 

• • • 

^^^^^^ - ^^^^^^^P^^^^^^^^^^^^^^B 

August 21, 1 hour after sunset 
Looking west-southwest 

Mars and Saturn dance with the star Spica during August, but be sure to 
pay attention when the Moon joins them on the 21st. Astronomy. Roen Keiiy 

binoculars, the planet-star 
combination will look like a 
wide double star. On August 1, 
Uranus lies 1.6° east-northeast 
of 44 Psc. The gap closes to 51' 
(0.85°) by the 31st. 

Larger binoculars (20x80, 
for example) or a telescope at 
low power will reveal a pleasing 

color contrast. The star shines 
at approximately the Sun's tem- 
perature, so it has a yellowish 
hue, while the planet glows blue- 
green courtesy of atmospheric 
methane. Increase the power on 
Uranus to see its 3.6"-diameter 
disk. Although this planet is 
about the same physical size as 

Comet C/201 1 F1 (LINEAR) rides high in the western sky after darkness 
falls as it slides through the central part of Bootes. Astronomy. Roen Keiiy 

Taurus when it peaks in mid-August. Unless we get an unexpected 
visitor from the distant Oort Cloud, we won't see any comets brighter 
than 10th magnitude before late winter. 

42 Astronomy -August 2012 

Locating asteroids 

Melpomene loops through the Serpent's tail 

The brightest asteroid on August evenings is 18 Melpomene. This 
86-mile-wide space rock plies the southwestern section of Serpens 
Cauda, the tail of the Serpent, near that constellation's border with 
Ophiuchus the Serpent-bearer. This region climbs highest in the 
south as darkness falls. Wait until the bright Moon leaves the eve- 
ning sky around August 4 to track the magnitude 1 0.0 Melpomene. 

Start your search at 2nd-magnitude Eta (n.) Ophiuchi in the lower 
left corner of the Serpent-bearer. Then, shift a finder scope's field of 
view to the east to your target. Melpomene remains within a couple of 
degrees of 4th-magnitude Omicron (o) and Xi (^) Serpentis all month. 

Note how the number of stars increases in the southern part of 
the field. With less obscuring gas and dust in this sector of the Milky 
Way, the distant lights shine through more easily. Of course, the 
higher star count also makes it harder to pinpoint the asteroid. 
Which point of light is it? You should be able to discern Melpomene 
from the pattern of stars on the finder chart. To be sure, plot the star 
field and label your suspect. Return to the same field a night or two 
later and confirm the asteroid by seeing which "star" moved. 

Neptune, it appears 50 percent 
bigger because it lies two-thirds 
as far away. 

The cavalcade of morning 
luminaries begins when Jupiter 
pokes above the horizon. This 
striking object rises shortly 
before 2 a.m. local daylight time 
August 1. Shining at magnitude 
-2.2, Jupiter lies 5° due north of 
1st- magnitude Aldebaran, the 
red giant star that marks Taurus 
the Bull's eye. A waning crescent 
Moon joins the pair August 11. 
The planet slowly crosses Tau- 
rus during August, ending the 
month in the middle of the Bull 
and rising shortly before mid- 
night local daylight time. 

Any telescope reveals Jupi- 
ter's disk, which grows from 36" 
to 39" across during August. 
Even small instruments show 
plenty of atmospheric detail. 
Look for a series of bright zones 
alternating with darker belts 
that run parallel to the giant 
planet's equator. Up to four 
bright moons join every scene. 
If you see fewer than four of 
these Galilean satellites, it 
means one or more of them 
is hiding in front of or behind 
the massive planet. 

The next planet on display 
is the only one brighter than 

Jupiter. Venus reaches greatest 
elongation August 15, when it 
lies 46° west of the Sun and rises 
more than three hours before 
our star. The brilliant planet 
dominates the morning sky, 
at least when the Moon isn't 
nearby. Venus gleams at magni- 
tude -4.6 at the beginning of 
August and fades only to mag- 
nitude -4.3 by month's end. 

On the 1st, Venus stands 2° 
south of 3rd-magnitude Zeta 
(Q Tauri, the southern horn of 
the Bull. Between August 5 and 

12, the planet crosses Orion the 
Hunter's raised arm. A crescent 
Moon joins Venus on August 

13, by which time the planet is 
tickling the feet of Gemini the 
Twins. Venus closes the month 
9° south of lst-magnitude Pol- 
lux, the Twins' brightest star. 

The period surrounding 
greatest elongation is always 
an exciting one for planetary 
observers. When viewed 
through a telescope this month, 
Venus shrinks and its phase 
waxes dramatically Over 
August's 31 days, its apparent 
diameter drops from 28" to 20" 
while its illuminated fraction 
grows from 42 to 58 percent. 

Mercury comes to greatest 
western elongation a day after 

• •• 

... N 

J * • . \Aug1 

*" * * i * 

• Path of Melpomene— \ 

. , o^t 11 

SERPENS * • • . I • • 
CAUDA * • • '.V 








m • 





• • 



i° •• 

A handful of bright guide stars in Serpens Cauda makes it fairly easy 

tO track Melpomene thiS month. Astronomy: Roen Kelly 

Capella . 

AURIGA Jupiter^ •" 


Castor* • Betelgeuse » • Rigel 


Mercury • •Procyon 

.re sunrise 

August 1 5, 45 minutes before sunrise 
Looking east 

A parade of planets lights up the dawn sky all month. Mercury and Venus 
reach greatest elongation on consecutive days in mid-August. Agronomy: Roen Keiiy 

Venus. But at an angular dis- 
tance of only 19° from the Sun, 
the innermost planet hugs the 
eastern horizon. Start looking 
for it around August 1 1. It then 
shines at magnitude 1.0 and 
rises about 80 minutes before 
sunrise. It quickly brightens, 
however, reaching magnitude 
-0.1 by greatest elongation 
August 16. That morning, it 
stands 10° above the horizon 
30 minutes before the Sun rises. 

Mercury grows brighter as 
the month progresses, partially 
offsetting its lower altitude. You 

should be able to track it until 
August's final week, when it 
reaches magnitude -1.0 but 
lies only half as high in the 
predawn sky. 

Mercury's telescopic appear- 
ance changes at a much faster 
pace than Venus'. When it first 
comes into view August 8, the 
innermost planet spans 9" and 
shows a 15-percent-lit phase. At 
greatest elongation, it displays a 
7"-diameter disk that is 42 per- 
cent illuminated. And a week 
after that, Mercury appears 6" 
across and 69 percent lit. * 43 

Mars mania 

Since antiquity, Mars has captured our minds and imaginations, 
and its study has led to important discoveries — and some of the 
greatest misconceptions — in planetary science, by Karri Ferron 

WW hen the ancient Greeks 
1 looked up at the night 
sky, they were fascinated 
by "wandering stars" that 
traced paths across the 
heavens. One in particular stood out: a red 
planete that briefly moved backward in a 
looping motion every two years before 
correcting its path. True, two other "stars" 
also reversed direction, but this one's 
movement was faster and therefore more 
pronounced. The Greeks named the 
bloody wanderer after their god of war, 
Ares — Mars to the Romans. 

Since then, the Red Planet has influ- 
enced more astronomers, generated more 
debate, and been the subject of more sto- 
ries than any other planet. But why has 
Mars created such interesting finds and 
fanciful facts? The answer lies in the Red 
Planets colorful relationship with Earth. 

Of gods and motions 

As many as 5,000 years ago, the Egyptians 
understood Mars' unique path through the 
sky and called it sekhed-et-em-khet-ket (one 
who travels backward). Most other cultures 
gave the reddish wanderer a more sinister 
name because such a motion signified dis- 
order and distrust. To the Babylonians, 
Mars was Nirgal (star of death), while it was 
Angakara (burning coal) in India. 

Of course, the two most common names 
associated with the planet were Ares and 
Mars, the gods who each had significant 
influence on the ancients. The Cult of Ares 
existed from the 1 1th century B.C. to the 
fourth century a.d. For the Roman Empire, 
Mars was its protector and the father of 
Romulus and Remus, the founders of Rome. 

But Mars' influence wasn't only mytho- 
logical. Its unusual retrograde path puzzled 
scholars. In the fourth century B.C., Eudoxus 

of Cnidus, a student of the Greek philoso- 
pher Plato, began studying this motion. He 
supposed that Mars moved as if it were a 
small rotating sphere pinned to the rim of a 
larger wheel; he was also the first to suggest 
the planet had a tilted axis of rotation. 

The Greek astronomer Ptolemy con- 
ducted numerous observations of Mars in 
the second century a.d. while trying to 
understand Aristotle's complicated model of 
55 solar system spheres. In the end, he made 
this "epicycle theory" even more complex. 
Still, he was able to calculate roughly the 
Red Planet's motion across the sky. 

Ptolemy's Almagest remained the 
authoritative text on astronomy through- 
out the Middle Ages. It wasn't until Tycho 
Brahe (1546-1601) that Mars' motion 
again began to cause a stir. Tycho studied 
the Red Planet closely at every opposition 
(when the planet lies opposite the Sun in 

Mars' retrograde motion around opposition 
intrigued observers even in ancient times. It also made 
understanding Mars difficult for many astronomers. 

44 Astronomy -August 2012 

Photo collage by Astronomy, Alison Mackey 

Earth's sky) after 1580. A year before he 
died, Tycho met Johannes Kepler (1571— 
1630) and assigned the German mathema- 
tician the task of understanding Mars' 
movement through the sky. 

After 10 years of work, Kepler developed 
his laws of planetary motion, which matched 
Tycho's observations of the Red Planet. 
Using a Sun-centered system with elliptical 
orbits, he could predict Mars' movement. 

A telescopic revolution 

Kepler released his results in 1609, the same 
year the Italian astronomer Galileo Galilei 
(1564-1642) pointed his rudimentary tele- 
scope skyward and began a renaissance in 
astronomy. It wasn't until the middle of the 
century, though, that a picture of the Red 
Planet became clearer. 

Much of that credit goes to Dutch 
astronomer Christiaan Huygens (1629- 
1695). In 1659, he noticed a triangle- 
shaped dark area across Mars' face. His 
sketch of what is today called Syrtis Major 
was the first such drawing of a martian 
surface feature. 

Using the shape as a guide, Huygens 
began an extensive record of how the Red 
Planet rotates, coming up with a rate of 24 
hours, the same as Earth. He also made a 
fairly accurate guess of Mars' size and wrote 
philosophically about the civilizations he 
believed lived on Mars and the other planets. 

Meanwhile, Italian-French astronomer 
Giovanni Domenico Cassini (1625-1712) 
also was observing martian surface features. 
He refined the Red Planet's rotation period 

▲ Ptolemy's epicycle theory of the second century b.c 
attempted to explain the motions of the planets. To describe 
that of Mars, the astronomer had the planet move uniformly 
about a point that then moved around Earth. Mary Evans picture Library 

► Johannes Kepler's laws of planetary motion, published in 
1609, were based on 10 years of studying Mars, a task assigned 
to him by fellow astronomer Tycho Brahe. To explain the path 
of the Red Planet and others, Kepler developed a Sun-centered 

System With elliptical OrbitS. Linda Hall Library of Science, Engineerings Technology 

Karri Ferron Is an Astronomy assistant editor. Writing about 
Mars' colorful past combined two of her favorite subjects: 
planetary science and as tronomical history. 45 

What is now known as Syrtis Major was one of 

the first identified surface features on Mars, 
sketched by Christiaan Huygens in 1659. 
Giacomo Filippo Maraidi continued Huygens' 
work, as shown in these four drawings. Syrtis 
Major is at the bottom right. 

to 24 hours and 40 minutes (todays known 
value is 24 hours, 37 minutes, 22 seconds). 
And during Mars' close approach to Earth in 
1672, he and his colleague Jean Richer used 
observations of the Red Planet to refine the 
distance between our planet and the Sun to 
within 6 million miles (10 million kilome- 
ters) of the correct measurement. 

Cassini's nephew Giacomo Filippo 
Maraidi (1665-1729) took up Mars next, 
studying the planet extensively until 1719. 

In 1704, he first observed white spots on 
both of the Red Planet's poles. By the 1719 
opposition, he suggested that the areas could 
be ice caps because the southern one grew 
and shrunk with the martian seasons. 

German-born English astronomer Wil- 
liam Herschel (1738-1822) confirmed 
Maraidi s finding during the 1777 opposi- 
tion and noted that the spots could be com- 
posed of water-ice. A few years later, while 
observing a close passage of Mars in front of 
two faint stars, Herschel concluded that the 
Red Planet must have a thin atmosphere 
because it had little effect on the background 
stars' light. He also discovered that Mars had 
an axial tilt of 30° (the correct value is closer 
to 25.2°), only slightly greater than Earth's 
23.4°, meaning the Red Planet had compa- 
rable seasons, only longer. 

Because Herschel, like Huygens, believed 
in inhabitants on other planets, he thought 
that those on Mars "probably enjoy a situa- 
tion in many respects similar to ours." Mar- 
tians didn't become menacing until later. 

Mapping Mars 

An image of Mars interspersed with blue- 
green patches, possibly oceans or vegetation, 

came to the forefront as 19th-century 
astronomers began to map the martian sur- 
face. The first to do so were Wilhelm Beer 
(1797-1850) and Johann Heinrich von 
Madler (1794-1874) in 1830. They used a 
small round patch just south of the true 
equator as their zero meridian, a marker 
martian cartographers still use today. 

The next significant drawings came 
from the Jesuit astronomer Pietro Angelo 
Secchi (1818-1878). He was the first to call 
Syrtis Major an ocean during the 1858 
opposition, and in 1863, he made an 
attempt to draw the complex color scheme 
he observed on Mars. Based on the various 
reds, greens, and blues, he wrote, "The exis- 
tence of seas and continents . . . has been 
conclusively proved." 

A year later, Reverend William Rutter 
Dawes (1799-1868) created 27 drawings of 
Mars, all so vivid that they inspired English 
astronomer Richard Anthony Proctor 
(1837 -1888) to use them for an 1867 map. 
The result would stand for two decades 
before one man's observations changed 
everyone's view of the Red Planet. 

The mystic canoli 

The year 1877 brought a Mars opposition 
that also came during the planet's closest 
point to Earth, making it the target of many 
astronomers. At the U.S. Naval Observa- 
tory, Asaph Hall (1829-1907) discovered 

William Herschel recorded the Red Planet's changing seasons in 1784. He believed they were 

Comparable tO thOSe On Earth, Only longer. Linda Hall Library of Science, Engineering & Technology 

Richard Anthony Proctor's map of Mars, 

published in 1867 and based on 27 drawings by 
Reverend William Rutter Dawes, stood as the 
pre-eminent chart of the Red Planet for more 

than tWO deCadeS. Michael E. Bakich library 

46 Astronomy -August 2012 

Giovanni Schiaparelli's late-1 9th-century map of Mars caused an uproar when he identified thin lines across the surface as canali. In Italian, this 
means grooves or channels, but the English translated the term as man-made canals. undaHau Library of science, Engineering & Technology 

two moons circling the Red Planet, which 
he eventually named Phobos and Deimos 
after the Roman gods of fear and panic, 
respectively. Meanwhile, Giovanni Virginio 
Schiaparelli (1835-1910) set out to map 
Mars' geography using an 8.6-inch refractor 
in Milan, Italy. He noted that the main con- 
tinents Proctor had drawn were actually 
multitudes of islands. But most 
importantly, he plotted an intri- 
cate network of linear features, 
which he named canali. 

In Italian, canali means 
channels or grooves; it is evident 
that this is what Schiaparelli meant based 
on his use offiume (rivers) as a synonym. 
But to the English, these features became 
man-made canals. 

Although Schiaparelli believed the chan- 
nels were natural, the idea that only intel- 
ligent life could create such intricate 
waterways ran rampant. Science-fiction 
author Camille Flammarions (1842-1925) 
1892 best-seller, La planete Mars et ses con- 
ditions d'habitabilite ("The planet Mars and 
its habitability conditions"), bespoke the 
Utopia of Mars and the influence of Schiapa- 
relli s work. "It would be wrong to deny that 
[Mars] could be inhabited by human species 
whose intelligence and methods of action 
could be far superior to our own," he wrote. 

"Neither can we deny that they could have 
straightened the original rivers and built a 
system of canals with the idea of producing 
a planet-wide circulation system." 

Finally, in 1893, Schiaparelli spoke out 
about the canali he discovered in La vita sul 
pianeta Marte ("Life on the planet Mars"): 
"It is not necessary to suppose them the 

would soon provide a "pretty definite dis- 
covery" about life on Mars. 

Lowell and his staff mapped more canals 
than any previous observers during the 1894 
opposition. He suspected that Schiaparelli's 
"oceans" had no water, which observations 
confirmed. Instead, he concluded that these 
dark areas were vast tracts of vegetation. 

In Italian, canali means channels or grooves. ... But to 
the English, these features became man-made canals, 

work of intelligent beings, and ... we are 
now inclined to believe them produced by 
the evolution of the planet." 

But it was too late. On Christmas Eve 
1893, Flammarions La planete Mars landed 
in the hands of the man who would become 
the most staunch supporter of the canals 
and life on Mars: Percival Lowell. 

Lowell's Mars 

After reading Flammarions book about 
the potential to find life on the Red Planet, 
wealthy American businessman Percival 
Lowell (1855- 1916) decided to make 
Mars his life's work. In 1894, he built a 
mountaintop observatory near Flagstaff, 
Arizona, for his research, believing he 

In one of the most influential books 
about the Red Planet (Mars, 1895), Lowell 
depicted the world as a desert similar to 
Arizona, with thin air and the occasional 
oasis. The straightness of the canals he saw 
meant they were artificial and created for 
martian survival after their planet had lost 
much of its water supply. 

But Lowell had many critics. Although 
not a vocal one, Edward Emerson Barnard 
(1857-1923) made observations that con- 
flicted with those made in Flagstaff. In 
1894, using the 36-inch Lick Refractor 
atop Mount Hamilton in California, Bar- 
nard failed to see any canals. Still, he did 
see mountains and plateaus, and he even 
suggested that Syrtis Major might be the 47 

/ /tW'17 /a % 

/ mm i it ani/ir 

'M //■•: if i 

#' I 


7 'J ' * 

Percival Lowell's Mars included more canals than any previous astronomer had observed. He also 
believed that the dark areas on the Red Planet were vast tracts of vegetation. Loweii observatory Archive 

Percival Lowell built an observatory in 
Flagstaff, Arizona, in 1894 for the sole purpose 
of searching for signs of life on Mars through a 

24-inch refractor. Lowell Observatory Archive 

latter instead of an area of vegetation 
(which is, in fact, true). 

Lowell's most vocal opponent, though, 
was Eugene Michel Antoniadi (1870-1944). 
During the 1909 opposition, the Greek- 
born French astronomer observed Mars 
through the 33-inch refractor at Meudon 
Observatory in Paris — the largest refractor 
in Europe. Instead of canals, he saw discon- 
nected patches of ridges and craters. The 
features Lowell and others claimed to see, 
he said, were only visible through a turbu- 
lent atmosphere that distorted the view. As 
Antoniadi wrote in a letter to colleagues, 
"The spider's webs of Mars are doomed to 
become a myth of the past." 

Mars attacks 

Despite this mounting opposition, Lowell's 
canals lived on into the 1960s, and the idea 
of life on Mars highly influenced popular 
culture. But unlike Lowell's martians, who 
were benevolent, the Mars of science fiction 
was full of war-loving inhabitants. 

The first to depict martians as monsters 
was H. G. Wells in War of the Worlds, pub- 
lished in 1897. The interplanetary war story 
details ruthless martians who invade Earth. 
Broadcast as a radio play more than four 
decades later, it would become the defining 
moment of Mars in science fiction. 

The most popular martian monsters of 
Lowell's time were the result of Edgar Rice 

While telescopic photographs of Mars improved between the 1 900s and 1 960s, the best ones were 
still blurry, so the existence of the canals remained inconclusive. Loweii observatory Archive (1900s and i93os),lpl(196os) 

Burroughs' (1875-1950) "Barsoom" series 
about the earthly hero John Carter. Bar- 
soom was the author's fictional representa- 
tion of Mars and was largely based on 
Lowell's observations — a civilization dying 
in the deserts — but Burroughs added six- 
legged green martians. 

In the 1920s, pulp magazines ushered in 
the golden age of science fiction. Although 
many young authors in these easily pro- 
duced tabloids were influenced by Lowell's 
Mars, they cared little for scientific fact. 
Meanwhile, with the invention of radio 
communication, claims of signals from 
Mars often occurred, fueling the lingering 
belief in life on the Red Planet. 

Then, in what has become one of the 
most famous radio broadcasts in history, 
Orson Welles (1915-1985) adapted War of 
the Worlds for his The Mercury Theatre on 
the Air series October 30, 1938. More than 
1.7 million people listened in as "news 
bulletins" told of martians invading Earth. 
Despite advance warnings that this was a 
fictional broadcast, the program brought 
panic, as many listeners tuned in late. 
Because inhabitants on Mars were still 

48 Astronomy -August 2012 

► Invaders from Mars capitalized on 
America's strong anti-communist 
sentiment in the 1950s by hiding evil 
martians in the minds of humans — 
analogous to the invisible threat of 

COmmUniSm. Mary Evans Picture Library 



H. G. Wells' War of the Worlds, published in 1897, first introduced 
martians as monsters. This illustration from a 1 906 reprint of the 
story shows the first alien emerging from its ship. 

< Ray Bradbury's The 
Martian Chronicles is considered one 
of the best science-fiction novels of all 
time. This 1951 collection of 27 short 
stories details the human fight to 
colonize Mars after fleeing a 

devastated Earth. Karri Ferron library 

theoretically possible and people relied on 
the radio to get their news about the 
unrest in Europe and the Pacific, listeners 
took the broadcast to heart. 

Cold War influence 

Mars and martians took a backseat during 
the height of World War II, but the fear 
caused by the ensuing conflict between the 
United States and the Soviet Union during 
the Cold War had a vast impact on humans' 
relationship with the Red Planet, both fic- 
tional and real. Parallels to the Red Scare 
(strong American anti-communism senti- 
ment) and the threat of atomic weapons 
seeped into the story lines of science-fiction 
novels and movies in the 1950s. 

In some films, like Invaders from Mars 
(1953), evil martians echoed Americas 
paranoia over an unknown enemy — these 
aliens could mask themselves as humans 
through mind control, making them just as 
unrecognizable as communists. In others, 
such as The Day the Earth Stood Still (1951), 
they were a benevolent society attempting 
to save Earth from the nuclear arms race. 

Meanwhile, the most famous Red 
Planet novel of the time was The Martian 
Chronicles, written as a collection of 27 
short stories for magazines by the cele- 
brated science-fiction author Ray Brad- 
bury and published into a book in 1951. 
He returned to the Mars of Lowell, with 
the planet's ecology somewhat conducive 
to life but faced with a near-extinct race. 

His earthly characters fight to colonize 
Mars after fleeing from an Earth devas- 
tated by atomic warfare. 

The Cold War also had great influence 
on real-life studies of the Red Planet. A 
major part of this conflict involved techno- 
logical competitions, including the space 
race. Artificial satellites launched in the late 
1950s indicated that unmanned exploration 
of other planets was possible. 

The Soviets were the first to endeavor 
to explore Mars in 1960, but the spacecraft 
failed to reach Earth orbit. Multiple subse- 
quent attempts resulted in similar out- 
comes. Then, in November 1964, the 
United States launched two Mariner 
spacecraft to perform flybys of Mars. 
Although Mariner 3 was lost, its sister 
craft reached its destination. And what it 
saw would completely change scientists' 
view of the Red Planet. 

The martian canals disappeared in July 1965 
with the arrival of NASA's Mariner 4, which sent 
back 22 postage stamp-sized images of a 
cratered world with no signs of life, nasa/jpl 

The truth revealed 

On July 15, 1965, Mariner 4 flew 6,1 18 
miles (9,846km) above the surface of Mars, 
capturing 22 postage stamp-sized photos to 
send back to Earth. The images showed no 
canals and no signs of life — only craters 
and plateaus. What Lowell had insisted he 
saw from Earth were in fact chains of crater 
walls — dots that, from a distance, blurred 
together to form lines. 

The impact craters made the martian 
surface look more like that of the Moon 
than of a world that was once possibly 
inhabited. Measurements of the Red Planet's 
thin atmosphere were also surprising. Mari- 
ner 4's radio signal indicated a surface pres- 
sure of between 4.0 and 5.1 millibars 
(thousandths of a bar, where 1 bar is about 
the surface pressure of Earth's atmosphere). 
Before the spacecraft's arrival, most esti- 
mates hovered between 85 and 87 millibars, 
with only one going as low as 25. Mars 
wasn't Earth-like at all. 

Today, we know Mars is much different 
from what scientists believed they had 
found in 1965 — another Moon. Still, those 
images put to rest a colorful and often fanci- 
ful picture of the Red Planet not based in 
reality. Astronomers now are using fresh 
discoveries to paint a new portrait of Mars 
— one just as exciting as the Red Planet of 
the past 5,000 years. « 


Explore more of Mars' colorful history 
at 49 

Ask Astro 

Astronomy's experts from around the globe answer your cosmic questions. 

Rocks from space 

Space rocks versus TNT 

Q a When a really big rock (or a huge chunk of iron) hits 
• Earth, why does it explode instead of just making a 
lot of rubble? — Bill Albertson, Ann Arbor, Michigan 

A 9 In 1924, Algernon Charles Gifford wrote in the somewhat 
• obscure New Zealand Journal of Science and Technology that 
meteorite impacts are profoundly different from the more 
familiar impacts of bullets because of the enormous 
energy objects moving at meteoritic velocities carry. He 
computed that a meteorite traveling at 7,200 mph (1 1,600 km/h) 
(and that's relatively slow — the average impact velocity on Earth 
is actually about 36,000 mph [58,000 km/h]) contains as much 
energy as an equal mass of TNT. (This is because energy is pro- 
portional to the velocity squared.) Gifford proposed that, at such 
speeds, the final crater is essentially blasted out as if by an 
explosion, rather than by simply pushing material aside. 

The energy content of impacting meteorites is larger than the 
energy required to melt or even vaporize the projectile com- 
pletely. While about half of this energy goes toward opening the 
crater, the remaining energy stays in the impactor and ultimately 
disperses it into tiny droplets of molten iron — as occurred at 
Barringer Meteorite Crater in Arizona — or even as rock vapor. 

In 1900, Daniel Moreau Barringer first investigated the site 
eventually named in his honor as a potential source for the 
nickel-iron he believed was buried beneath the crater floor. 
Despite vigorous attempts to locate the supposed mass of iron, 
none was ever found. Finally, in 1946, meteoriticist Henry H. 
Nininger recognized that small pieces of iron scattered outside 
the crater were all that remained of the projectile. — JayMelosh, 
Purdue University, West Lafayette, Indiana 

- 100,000,000 

- 1,000,000 

Cretaceous-Tertiary (K/T) 

World's nuclear arsenal 

Nuclear winter 

1-1,000 Meteorite Crater 






Once every 



Once every Once every 
million 100 million 





A space rock hurtling toward Earth at speeds of several miles per hour 
contains as much energy as an equal mass of TNT, and thus explodes at 
our planet's surface. This diagram compares how frequently impacts of 

equivalent TNT energy OCCUr. Astronomy: Roen Kelly, after Alan Harris 


Q t I read recently about the possi- 
• bility of two white dwarfs collid- 
ing to create a type la supernova. 
Why do astronomers think it has to be 
two white dwarfs instead of a white 
dwarf colliding with a regular star? 
— Steven Smith, Charlotte, North Carolina 

A 9 We have known for a while now that 
• a type la supernova comes from a 
white dwarf that has exceeded the "Chan- 
drasekhar" mass limit — nearly 1.4 times 
the Suns mass. Astronomers have two 
theories of how the white dwarf can get to 
that mass, and both say that the star must 

interact with a companion sun of some sort 
to gain material and reach this limit. This 
companion has one of two possible identi- 
ties: It can be another white dwarf or a reg- 
ular star (like a red giant). In both cases, the 
two stars were in a binary orbit with each 
other long before one (or both) became a 
white dwarf, and likely since they were 
born. (Due to the extreme vastness of 
space, two disconnected stars randomly 
colliding with each other would be an 
incredibly rare occurrence.) 

In the case of two white dwarfs, the 
two stars spiral closer and closer, giving 
of f gravitational radiation, until they 
collide. If their combined mass is greater 

than the Chandrasekhar limit, the collision 
will result in a type la supernova. 

In the case of one white dwarf and a 
regular star, as the stars evolve and 
begin to spiral closer to each other, 
they reach a point where mass transfer 
begins. The white dwarf's gravity is very 
strong, and the outer layers of the regular 
star are not tightly bound, so the white 
dwarf is able to pull gas from the regular 
star onto its surface. This mass transfer 
stabilizes the orbit so that the two 
stars no longer move closer to each 
other and will not collide, as in the 
case of the two white dwarfs. Instead, 
the white dwarf can accumulate so much 

50 Astronomy -August 2012 

The most distant galaxy observed (UDFj-39546284, 
from 480 million years after the Big Bang) 

A mature spiral galaxy within the Coma cluster 
(NGC 491 1 , some 320 million light-years from Earth) 



w*- KV --jfl - 3B^H|^C 

3£ = 

13 -^ £ S 




Galaxy complexity and evolution varied over the history of the universe. In early eras (left), the cosmos was much denser, so protogalaxies — small 
clumps of dark matter and gas — could form more quickly. These small protogalaxies merged and became more massive, eventually forming the large 
galaxies of today (right), which also contain richer details and structure than the first galaxies. 

mass from its companion that it reaches the 
Chandrasekhar mass limit and explodes as 
a type la supernova, leaving its companion 
star behind. If we don't find a star near the 
supernova remnants center, we can assume 
the explosion came from two white dwarfs. 
— Ashley Pagnotta, Louisiana State University, Baton Rouge 


Q t The Hubble Space Telescope 
• found a galaxy that was com- 
pletely formed within 480 million 
years of the Big Bang. How could gas 
and dust clouds condense into stars 
and organize themselves via gravity 
into an entire galaxy in less time than 
it takes the Milky Way to make two 
rotations? — Mike Palmer, Kitchener, Ontario, Canada 

A Galaxies like the Milky Way 
• indeed could not have formed as 
a unit at such an early era after the Big 
Bang. The time span for sufficient dark 
matter and gas to collect into a unit bound 
by gravity and with active star formation 
would be too long. 

So what do we think happened in these 
early times? The universe was much denser 
(likely by a factor of more than 1,000) when 
dark matter began to make the first seeds of 
galaxies. The first galactic objects were 
smaller and denser than present-day 
galaxies, and thus could collapse and 
pull in gas on timescales of tens, rather 
than hundreds, of millions of years. 
Once gas compressed inside such a 
protogalaxy, stars could begin to form 
— an especially tricky step that is not 

fully understood — and then galactic 
evolution could proceed quickly. For 

example, very massive stars burn their 
nuclear fuel in less than 3 to 5 million years 
and explode as supernovae, spewing out 
newly synthesized atomically heavy chemi- 
cal elements. These "metals" foster gas- 
cooling and, thus, more star formation — 
and the protogalaxy is up and running. 

The dense dark matter needed to pro- 
mote collapse was produced by disturbances 
in the early universe. As the post-Big-Bang 
cosmos cooled, the uneven density of dark 
matter became important: The densest 
places were first to resist cosmic expansion 
and collapse under their own gravity. We 
do not see these protogalactic seeds today. 
Over time, most of these early objects 
merged with their neighbors and became 
more massive, eventually being incorpo- 
rated as small parts of the giant galaxies 
we observe today — like the Milky Way. 
— Jay Gallagher, University of Wisconsin-Madison 


Q # Is it possible that the gravitational 
• effects attributed to dark matter 
could be caused by Jupiter-sized plan- 
ets discovered orbiting other stars and 
also floating freely outside planetary 
systems? — Martin J. Grumet, Boise, Idaho 

A # The current number of detected 
• Jupiter-sized planets either gravita- 
tionally bound to a central star or free- 
floating is large, and the count is increasing. 
The gravitational effects of these worlds on 
other planets could be substantial, but for 

the most part such dynamic interactions 
are confined to their nearby environs. 

Ordinary, or baryonic, matter — like the 
material from which these planets form — 
interacts with photons to produce scattering, 
emission, or absorption against luminous 
sources. Dark matter, which is composed of 
nonbaryonic subatomic particles, does not 
interact with light in the same fashion. 

A large number of detected and 
undetected Jupiter-sized planets 
could not mimic the gravitational 
effects produced by dark matter for 
two reasons. First, planets, although 
faint, are made of luminous matter 
and therefore are ultimately detect- 
able. Second, their estimated num- 
bers and locations, primarily around 
the galactic plane, do not support the 
large-scale gravitational effects simi- 
lar to those of dark matter (like the 
ones explaining galactic rotation or the 
large-scale bending of light, called gravita- 
tional lensing). 

Given the proper geometric alignment, 
however, Jupiter-sized planets could pro- 
duce localized and temporary signal 
increases from background sources, a phe- 
nomenon known as the microlensing effect. 
This is precisely the mechanism by which 
we first detected free-floating planets. 
— Mario Perez, NASA Headquarters, Washington, D.C. 

Send your questions via email to: askastro@; or write to Ask Astro, P. O. Box 
1612, Waukesha, Wl 53187. Be sure to tell us 
your full name and where you live. Unfortunately, 
we cannot answer all questions submitted. 51 

aging heave 

Astrophotographer Wally Pacholka has made an art of capturing 
amazing landscapes and skies. All photos by Wally Pacholka 

f * 


During the wee morning 
hours of a Canadian 
winter day in 1958, my 
parents heard again a 
mysterious sound on the 
roof. Eventually, my dad went to check 
what was going on. Finding me on the 
second-story fire escape, he asked, 
"What are you doing, Wally?" I an- 
swered, "Dad, I enjoy looking at the 
stars! Don't you?" 

My dad didn't know what to make of 
the whole situation, but my parents 
soon discovered that their son had a 
strong interest in the stars and planets. 
A few years later, with paper route 

Wally Pacholka is a member of the 
international astrophotography team The 
World at Night (TWAN). His specialty is 
shooting the national parks at night. For 
more information, visit 

money, I purchased a camera at a pawn 
shop and began to show my parents 
and six brothers and sisters — who all 
thought I was "some kind of nut" — 
photos of the things I was seeing in the 
night sky while they 
slept. My equipment was 
pretty basic: a 35mm 
camera, standard 50mm 
lens, and a tripod. I'd 
been taking exposures of 
about 30 seconds. 

Today, many decades 
later, I still use a 35mm 
camera (a Canon 5D 
DSLR) with a tripod, 
slightly shorter exposure 
times, and no lens with a 
focal length longer than 50mm. But 
now, amazingly, my photos are for sale 
in the gift shops at Palomar Observatory 
in California, the Keck Observatory on 

Hawaii's Mauna Kea, Kitt Peak National 
Observatory in Arizona, and through- 
out the Western national parks. They've 
appeared in publications like Astron- 
omy, National Geographic, and TIME 
magazine, as well as 
online at NASA's Astron- 
omy Picture of the Day. 
For 10 years now, taking 
star photos has gone from 
being my lifetime hobby 
to granting me a career as 
a "professional amateur 

Wally Pacholka 

Taking star photos has gone from being 

my lifetime hobby to granting me a career as 

a "professional amateur astronomer!' 

Landscape love 

From the onset, I always 
liked the idea of captur- 
ing both the night sky and the terres- 
trial landscape in a single shot. This 
method was just a simple extension of 
how I naturally saw the night sky with 
my unaided eyes. We don't see the Big 
Dipper in the sky by itself; we see it over 
the neighbor's house or rising above a 
lake. This technique, self-taught by 
countless amateur astronomers the 

52 Astronomy -August 2012 


The Milky Way stretches from the Southern Cross (at right) to the Northern Cross in this shot from Hawaii's Ma una Kea. 

Orion the Hunter rises over Utah's famous Rainbow Bridge National Monument on Lake Powell (arch lit by flashlight). 53 

Lessons learned 

Over the years, I've learned a thing or 
two about landscape astrophotogra- 
phy. Here are a few tips that you might 
find helpful, though you should never 
be afraid to experiment and discover 
for yourself what works best in a par- 
ticular situation. 

■ Location, location, location. If you 

want to take beautiful photos, you must 
go to beautiful places. Staying home 
and shooting the stars between the 
telephone wires in your backyard won't 
get your photos into TIME magazine or 
a national park's gift shop. 

■ Take care in composing the shot. 

Capture interesting features in both the 
night sky and on the ground. That way 
you get a double win. 

■ It might be easier than you think. 

Sometimes it all comes down to having 
the guts to get out there and do what- 
ever it takes to get that one-of-a-kind 
shot. Today's digital cameras are light- 
years ahead of anything offered just a 
short time ago, and it's possible to do 
today in 1 minutes what took me 1 
years to learn. 

■ Know your equipment. All of 

today's cameras have a zillion settings in 
auto mode, but only four settings in 
manual mode: exposure, f/stop, ISO, and 
focus. Start by setting your camera to 
manual mode and trying a 30-second 
tripod-mounted exposure. If that doesn't 
work, experiment with different times 
until you get pinpoint stars. Use the wid- 
est f/stop to get the most stars, but if 
they look like seagulls, cut back the 
f/stop until they appear sharp again. An 
ISO of 1 600 works well on most cameras, 
but if it doesn't on yours, work to find 
your camera's sweet spot. The proper 
focus is easiest of all to determine: The 
stars are more than 200 feet (60 meters) 
away, so just use the infinity setting. 

■ Learn the essentials of photo- 
graphic techniques. To summarize: 
For a film camera, try something like 

— Continued on page 56 


Mars shines over a rare moonbow from Hawaii's Haleakala Crater. 

From the onset, I always liked 

the idea of capturing both the night sky and the 

terrestrial landscape in a single shot. 

world over, is now officially known as 
landscape astrophotography. 

After my dad moved the family to 
Southern California in 1965, my night 
sky easy-access viewing was gone. But 
despite living in the bright Los Angeles 
area, I soon discovered the beauty of the 
local deserts, along with the value of 
nearby national parks (such as Joshua 
Tree and the Mojave National Preserve). 

As filmmaker and historian Ken 
Burns says, our country's national parks 

are "Americas gift to itself?' This is par- 
ticularly true for amateur astronomers, 
as the parks, especially the ones in the 
West, offer unparalleled beauty and pris- 
tine dark night skies. The combination of 
heavenly and earthly delights is unbeat- 
able for landscape astrophotography. 

Safety first 

Doing what I do is rewarding and fun, 
but it's not always easy or safe — kind 
of like the icy rooftop night-sky 

54 Astronomy -August 2012 

The Milky Way looms over Palomar Observatory in California. Here, the landscape is lit by surrounding cities hidden behind clouds. 

Old Faithful erupts in Wyoming's Yellowstone National Park 
(illuminated by local hotel parking lights). 

Sequoia National Park in California boasts a view featuring 
Venus, Orion, and their reflections in Hume Lake. 

Starkweather Lake in the Mammoth Lakes region of California's Eastern Sierra 
National Preserve reflects Jupiter and the stars of the Milky Way. 55 

Lessons learned 

— Continued from page 54 

Fuji 800 film, with a 30-second 
exposure, as near to f/2 as possible, and 
a 50mm, 35mm, or 24mm lens (no 
zoom lenses, which are generally not 
fast enough). This will record every star 
visible to the unaided eye. I left my film 
camera behind in the past century and 
now use a digital camera, setting the 
ISO to 1 600, the f/stop to f/2.2, and tak- 
ing a 25-second exposure through a 
24mm lens or a 20-second exposure 
with a 35mm lens. 

■ Lighting is critical in any good 
photograph. If you want your fore- 
ground subject to be visible and not 
appear as a silhouette, then you must 
figure out a way to light it. Unless the 
composition features nearby city lights 
(as in my Palomar Observatory picture 
at the top of page 55), you should get 
your shooting schedule to coincide 
with a crescent Moon, so it can light 
up your foreground (as in my Devils 
Tower photo at right). One approach I 
use is illuminating close foreground 
objects like rocks or hills with a flash- 
light while taking the star shot (as in 
my Rainbow Bridge shot at the bottom 
of page 53). 

■ Embrace the power of panorama. 

Perhaps the most powerful tip I can 
offer is to transform your 1 2-megapixel 
35mm camera into a 100-megapixel 
tool simply by shooting a panoramic 
sequence of side-by-side shots. Each 
one should include both the sky and 
land as you cover the entire horizon 
before you. Then, you can stitch the 
individual shots together using digital 
panoramic software. 

■ Above all else, have fun! No one 

is born a perfect photographer, so just 
go out and capture whatever you're 
most passionate about. I have discov- 
ered that I am really good at going to 
great lengths to be in the middle of 
nowhere in the middle of the night 
with no one else around. Whether it's 
on an icy rooftop or in a national park, I 
see it as my mission to show others the 
beauty I find there. — W. P. 

A monster Geminid meteor streaks over the Mojave Desert in California. 

Devils Tower National Monument in Wyoming, lit by moonlight, stands before the Milky Way. 

viewing that my dad had to put a stop 
to. In order to photograph national 
park landmarks at night, I need to 
actually hike the parks at night, usually 
alone. (After all, who would be crazy 
enough to join me as I drive 500 miles 
[800 kilometers] to one location, shoot 
all night, and then go 300 miles 
[500km] to the next location?) 

Folks say I should write a book 
about my nighttime close encounters, 
which include bears, snakes, large cats, 
small cats, skunks, porcupines, bugs, 
tarantulas, bears, unknown creatures 
walking in the shallow water toward 
me, green eyes looking at me from the 
darkness, and did I mention bears? 
Add in the fun of getting lost about a 

56 Astronomy -August 2012 

.;■ . g ■. i 

The sky over Hawaii's Haleakala Crater at sunrise reveals Scorpius, Alpha (a) and Beta (\'i) Centauri, and the Southern Cross. 

zillion times, and it's clear some 
nights will be a little bit more exciting 
than others. 

My most unforgettable experience 
was on a shoot at one of the darkest 
sites on Earth, imaging the stars with 
my associate Babak Sedehi over the 
huge Moai stone statues on Chile's 
Rapa Nui (Easter Island). It was just 

The Milky Way rises over California's scenic Manzanita Lake in Lassen Volcanic National Park. 

Despite living in the bright Los Angeles area, 
I soon discovered the beauty of the nearby deserts. 

past midnight, and I had two cameras 
going; I manually took close-ups of the 
statues with one and had the other 
automatically taking 30-second shots of 
the whole area from about 50 yards off. 
Suddenly, out of the distant darkness, 
we heard something shouting, "Furo! 
Furo! Furo!" We looked up to see a 
frightful, tattooed, nearly naked figure 
walking toward us throwing stuff. 

We didn't know what he was saying, 
but Babak got the message loud and 
clear, and he screamed at me, "Run! 
Wally, run!" Babak ran straight for the 
car, which was about 300 yards away, 
but I had to grab all of my scattered gear. 
I fell once but managed to keep going as 
our assailant's projectiles landed nearby. 

Babak had the car running (he was 
in full getaway mode) and swung the 
door open for me as I arrived. But, 
because I was carrying two camera tri- 
pods with six legs going every which 
way, I had trouble getting in. 

Finally, I forced my way through. 
Unfortunately, a tripod leg kept the 
door open, and I almost flew out as 
Babak rounded the first corner. Both of 
us were scared out of our wits until the 
bed and breakfast manager calmly told 
us, "Oh, that's Fetu. He's the assigned 
security guard out there!"* 



See more of the author's wide- 
field imagery online at 57 

Deep-sky observing 

Explore the Summer Triangle 

Although you'll never see Mars within the area bounded by these three bright stars, you can explore 
double stars, nebulae, and star clusters, by Michael E. Bakich 

From June through October in the 
Northern Hemisphere, the three 
stars of the Summer Triangle ride 
highest. Top dog is Vega (Alpha 
[a] Lyrae), the fifth-brightest star 
in the night sky. At magnitude 0.03, it has 
long been astronomy's standard zero- 
magnitude star. Altair (Alpha Aquilae), the 
12th-brightest star, glows with half Vega's 
output at magnitude 0.77. Last, but only 
least when compared to its two compan- 
ions, magnitude 1.25 Deneb (Alpha Cygni) 
comes in as the 19th -brightest star, one- 
third as bright as Vega. 

The region bounded by the Summer 
Triangle contains enough deep-sky treats to 
keep you observing for many hours. Let's 
examine a few of them. 

Start in the Harp 

Begin by pointing your telescope midway 
between Sheliak (Beta [(3] Lyrae) and 
Sulaphat (Gamma [y] Lyrae) to find the 
Ring Nebula (M57). Through a 4-inch tele- 
scope, you'll see the Ring as a pale gray ball 
71" across with a magnitude of 8.8. If you 
use a magnification above lOOx, you'll 
notice that the ball's outer part looks 
thicker than the central region. This gives 
M57 its distinctive "ring" appearance. 
Even for large-scope users, spotting 
M57 s central star ranks as a difficult 
observing challenge. With a 16-inch or 
larger instrument on a night of excellent 
seeing, use an eyepiece that yields between 

The Ring Nebula (M57) in Lyra shows the outer 
layers of a Sun-like star puffed off in the late 

Stages Of itS life. Mark Hanson 

300x and 400x. Keep in mind that you're 
searching for a 15th-magnitude star against 
a background that's not completely dark. 

If the central star doesn't show itself 
immediately, lightly tap on the tube. 
Because the eye is sensitive to motion, you 
may spot the central star at this point. 

You'll find the next object a bit more 
than 5.5° east-southeast of M57. It's globu- 
lar cluster M56, which, at magnitude 8.4, 
shows up in binoculars from a dark site. 

Through a telescope, the density of stars 
in M56 increases dramatically as you move 
toward its core. And because the individual 
cluster stars aren't all that bright, you'll 
resolve them best through 8-inch or larger 
telescopes and at magnifications exceeding 
150x. When you're done examining the 
inner workings of M56, back off the power 
and enjoy the star field this cluster is in. 

Now target Delta (8) Lyrae to observe 
the open cluster Stephenson 1 , also known 
as the Delta Lyrae Cluster. This is a pretty 
sight through even a 3-inch scope. Powers 
around 50x will split the standout suns in 
this cluster, Delta 1 and Delta 2 Lyrae, easily. 
The former is a blue magnitude 5.6 star 
while its companion (some 10' away) is an 
orange luminary shining at magnitude 4.5. 
The rest of the cluster counts 50 stars of 
various brightnesses. 

Our last object in Lyra is the gorgeous 
open cluster NGC 6791 , which lies less than 
1° east-southeast of magnitude 4.4 Theta 
(0) Lyrae. Its diameter of 15' — nearly half 
that of the Full Moon — means that, even 
at magnitude 9.5, NGC 6791 appears faint 
through small scopes. In fact, you may be 
fooled into thinking it's a globular cluster. 

Through 12-inch and larger instru- 
ments, NGC 6791 begins to strut its stuff. 
Dozens of faint cluster stars begin to 
resolve into a fine, evenly distributed pile 
of diamond dust. 

Explore Cygnus 

In the center of the Summer Triangle, you'll 
find Albireo (Beta Cygni), one of the sky's 

The Crescent Nebula (NGC 6888) reveals the 
interaction between a cloud of gas and a star's 
radiation and stellar wind. Ken Crawford 

finest double stars through any size tele- 
scope. The primary star shines golden at 
magnitude 3.4 while its companion glows 
sapphire-blue at magnitude 5.2. A healthy 
35" separate the two. 

Our next object, the Crescent Nebula 
(NGC 6888), is a bubble of gas carved out 
of the interstellar medium by an energetic 
sun called a Wolf-Rayet star, after the two 
astronomers who identified the type. It 
shines at 7th magnitude at NGC 6888's cen- 
ter. The Crescent lies 1.2° west-northwest of 
the magnitude 4.8 star 34 Cygni. 

Although you'll spot the Crescent Neb- 
ula through small scopes, 8-inch and larger 
instruments begin to show some of its 
structure. The slightly curved northwestern 
edge is the brightest, but a short line of 
bright nebulosity also lies to the southwest. 

From the Crescent, move a bit more 
than 2° east to M29. Although this target is 
a Messier object, it's one of the most diffi- 
cult to identify. The reason is that M29 is a 
loose open cluster of about two dozen stars 
lying in front of a rich Milky Way star field. 

To find it, look 1.8° south of magnitude 
2.2 Sadr (Gamma Cygni). A small telescope 

Michael E. Bakich is an Astronomy senior edi- 
tor and author of 1 ,001 Celestial Wonders to 
See Before You Die (Springer, 2010). 

58 Astronomy -August 2012 

The Dumbbell Nebula (M27) has a high surface 
brightness, so even small-telescope owners can 

enjoy it. Joe and Gail Melcalf/Adam Block/NOAO/AURA/NSF 

works best on this cluster because it won't 
reveal the multitude of surrounding stars. 
To prove this to myself, I once made a card- 
board insert for the front of a 12-inch tele- 
scope. The insert had a 3-inch-diameter 
hole in it, which I had carefully cut out. I 
viewed M29 with and without the insert, 
and the cluster was, indeed, easier to pick 
out when the insert was in place. 

Poor Aquila 

Because the Summer Triangle's stars come 
from three constellations, you should 
assume that Aquila brings something to the 
table. Alas, such a small area of the Eagle 
lies within the triangle that we can attribute 
no deep-sky treats to this constellation. 

Still, I didn't have the heart to totally 
exclude Aquila, so, ever-so-slightly outside 
the bounds of the triangle, look for one of 
my all-time favorite binocular objects. Bar- 
nard's E, a combo of two dark nebulae from 
American astronomer Edward Emerson 
Barnard's famous catalog, lies against the 
rich Milky Way. Start at yellow magnitude 
2.7 Tarazed (Gamma Aquilae). If you cen- 
ter that star, you shouldn't have to move 
your binoculars at all. Barnard's E lies 1.4° 
to the west-northwest. 

Barnard 143 (often designated B143) is 
the easiest of the pair to spot. It's a narrow 
bar about 15' long, oriented east- west. Two 
slightly less distinct dark bars connect to it 
and form a U shape. Just to the south lies 
Barnard 142 (B142), another dark nebula 
not quite as long and only one-third as 
wide, making it more difficult to see. 
Behind these dark clouds, you'll see the 
light of thousands of unresolved stars. 

Bonus entries 

The three constellations already discussed 
don't completely cover the area of the Sum- 
mer Triangle. In fact, you'll find half of 


. .--; *0 .Stephenson 1»/ 


M56® * ./ / 

r / 

VULPECULA * \ . • / . 

E ' . • .' v -* ■ i a '' • . 

.... *. . V--A- . . .•; . / : .• • . 

... \: M27 . / % • • . . 

• •.* \ . • * /. Coathanger * '• 


l * */ 

• f* .T o, 

Barnard's E 


Use this finder chart to locate all the objects discussed in this story, astronomy Richard Takott and RoenKeiiy 

Vulpecula the Fox and almost all of Sagitta 
the Arrow in our chosen area. 

Our next object is an easy one to spot 
through binoculars. Extend a line south- 
ward from Albireo in Cygnus through 
magnitude 4.4 Alpha Vulpeculae. That dis- 
tance is roughly 3°. Head 4.5° farther south, 
and you'll encounter Collinder 399. 

This group was the 399th entry (out of 
471) in a catalog of open clusters compiled 
by Swedish astronomer Per Arne Collinder. 
Its most common name, the Coathanger, 
comes from its shape. 

Because it's so big, the Coathanger looks 
best at magnifications of 20x or less. Ten 
stars glow brighter than 7th magnitude, so 
the group appears as a distinct glow to the 
naked eye on dark nights. The brightest are 
4 Vulpeculae, at magnitude 5.1; 5 Vulpecu- 
lae, at magnitude 5.6; and 7 Vulpeculae, 
which shines at magnitude 6.3. 

For my final object, I'd be hard-pressed 
to leave out the Dumbbell Nebula (M27), a 

great object for small-scope owners. You 
can find it by drawing a line from Altair to 
Sadr. M27 lies slightly less than halfway 
from your starting point. 

M27 owes its common name to a 
double-lobe shape common among plan- 
etary nebulae. Even through binoculars, 
this object is easy to spot. To see details in 
it, however, set up your telescope. 

A 4-inch scope shows the two bright 
lobes and several stars scattered across 
M27's face. This object responds well to 
high magnifications because it has a high 
surface brightness. Use a large telescope 
with an Oxygen-III filter and really crank 
up the magnification. 

After a night or two hunting objects 
within the Summer Triangle, you'll see 
those three stars in a whole new light, it 



To see additional images of deep- 
sky objects in the Summer Triangle, 
head to 59 

Amateur astronomy 


best dark-sky 
sites in the U.S 

Searching for a place to set up your telescope? A top-notch location might be closer than you think. 
by Michael E. Bakich 


ie-hard amateur astronomers aren't the only ones who 
want a dark observing site. It could be that you 
recently purchased your first telescope, and you're 
dying to know how well it can perform under optimal 
conditions. Unfortunately, you live in a metropolitan 
area where just catching the Moon in the sky is an accomplish- 
ment. Take heart! As this map shows, you'll find great observing 
locations throughout the contiguous United States. 

Some are the sites of star parties, three- to nine-day annual 
events where amateurs — as well as the public — gather under a 
dark sky. Others are sites managed by and for local astronomy 

clubs. Become a member and you'll gain immediate access to a 
dark site. Still others are communities set up specifically for ama- 
teur astronomers where you can lease or purchase lots. 

Whichever location you choose, you will experience a great 
limiting magnitude (the faintest star you can see) and good seeing 
(the steadiness of the atmosphere above you). Just remember to 
check the weather forecast before you go. No site is good enough 
to overcome clouds. 

Michael E. Bakich is an Astronomy senior editor who has observed at 
most of the sites on this map (and lots more). 

^} Cherry Springs State Park 
Location: near Galeton, 
Open: year-round 
Hosts: the Cherry Springs Star 
Party; the Black Forest Star Party; 
Music and Stars programs featur- 
ing concerts followed by an hour 
of stargazing (requires admission 
fee); free public programs 
Note: The International Dark-Sky 
Association named it the second 
International Dark Sky Park on 
June 11,2008. 

^% Green Bank Star Quest 
Location: Green Bank, 
West Virginia 

Open: once a year for a four-night 
star party 

Note: Organizers bill the Star 
Quest as the largest optical and 
radio star party in the nation. Reg- 
istration includes campsite and 
shower facilities, 

^J Deerlick Astronomy Village 
Location: Sharon, Georgia 
Open: to individuals who buy an 

annual field membership; 1.5-acre 
plots for cabins or houses are 
available on these 96 acres 
Hosts: the Peach State Star Gaze 
Note: As of this writing, only four 
sites remain available. 

III Chiefland Astronomy 
Location: 7 miles south of 
Chiefland, Florida 
Open: to members, and to visitors 
approximately 1 days per month 
for $5 per night 
Hosts: the Chiefland Star Party 

^ Winter Star Party 
Location: on Scout Key in the 
Florida Keys 

Open: once a year for a weeklong 
star party 

Note: This location has the most 
southerly latitude — 24°38'58.2" 
— of any dark-sky site on this 
map. From here, Acrux (Alpha [a] 
Crucis), the southernmost bright 
star in Crux the Southern Cross, 
sits right on the horizon, and the 
globular cluster Omega Centauri 
(NGC 5139) stands 1 8° above the 

southern horizon at its highest. 

^J Great Lakes Star Gaze 

Location: River Valley RV Park in 
Gladwin, Michigan 
Open: once a year for a four-day 
star party 

Note: In addition to sites at the RV 
park, you'll find available lodging 
at five nearby locations. Registra- 
tion discounts are available to 
those signing up before the 
posted deadlines, 

^y Hobbs Observatory 

Location: Beaver Creek Reserve 
near Fall Creek, Wisconsin 
Open: year-round to members of 
the Chippewa Valley Astronomical 
Society (CVAS) and guests 
Hosts: the Northwoods Starfest, a 
three-day event in late summer 
Note: The CVAS conducts monthly 
club meetings (except during 
December) that include programs 
and observing and are open to 
the public. 

Open: once a year for a five- to 

seven-day star party 

Note: hosted by the Astronomical 

Society of Kansas City 


^J Nebraska Star Party 
Location: Snake Campground, 
Merritt Reservoir, 27 miles south 
of Valentine, Nebraska 
Open: once a year for a weeklong 
star party 

Note: A Nebraska State Park 
entrance permit ($4 per day; $20 
per year) is required on all vehi- 
cles entering the observing field. 
A $7 per day fee also is required if 
you are camping in the park. 

^p Okie-Tex Star Party 
Location: Camp Billy Joe, 1 mile 
east of Kenton, Oklahoma 
Open: once a year for a nine-day 
star party 

Note: The event is hosted by the 
Oklahoma City Astronomy Club. 
The club allows school groups 
that preregister to attend. 

^J Heart of America Star Party l|l Rocky Mountain Star Stare 

Location: near Butler, Missouri Location: private land roughly 6 

60 Astronomy -August 2012 

miles north of Gardner, Colorado 
Open: once a year for a five-day 
star party in June or early July 
Note: The Colorado Springs Astro- 
nomical Society hosts this event, 
which features speakers, kids' 
activities, door prizes, and more. 

^ Texas Star Party 

Location: Prude Ranch, 5 miles 
north of Fort Davis, Texas 
Open: once a year for a weeklong 
star party 

Note: Prude Ranch offers tent 
camping, trailer/RV sites, bunk- 
houses that sleep eight to 20, and 
family cabins that sleep two to 
four. Because of high demand, 
organizers of the Texas Star Party 
conduct a random drawing in 
January to choose that year's 
actual attendees. 

Q) Double U Ranch 
Location: near Cornudas, Texas 
Open: year-round to members 
and guests of the Sun City 
Astronomers (SCA) 
Note: The SCA meets monthly in 
the Gene Roddenberry Planetar- 
ium, 6531 Boeing Drive in El Paso. 


ffE Enchanted Skies Star Party 
Location: Socorro, New Mexico 
Open: once a year for a four-day 
star party 

Note: offers tours of the Karl G. 
Jansky Very Large Array and a 
night of observing at the Magda- 
lena Ridge Observatory, which 
sits atop South Baldy at an eleva- 
tion of 10,600 feet (3,230 meters) 

ffl Granite Gap 
Location: 13 miles north- 
northwest of Animas, New Mexico 
Open: year-round to lessees and 
for site inspection visits by indi- 
viduals wishing to lease plots 
Note: Leases are available for 
te-acre plots on which you can 
park a camper or erect an obser- 
vatory. Rental units are available 
for extended stays. 

^^ Russell Country Star Party 
Location: Lewis and Clark 
Interpretive Center, Great Falls, 
Open: monthly on Friday nights 

closest to New Moon, weather 

Note: The Central Montana 
Astronomy Society, with coopera- 
tion from the U.S. Forest Service, 
hosts these events, which include 
refreshments, indoor kids' activi- 
ties, free admission to the Lewis 
and Clark Center, and more. 
listings/1 51 77.htm 

^p Grand Canyon Star Party 

Location: the North and South 
rims of Grand Canyon National 
Park in Arizona 

Open: once a year for a weeklong 
star party 

Note: Volunteers set up their tele- 
scopes for park visitors. Admission 
for seven days is $25 per private 
vehicle or $12 per individual. 

^y Table Mountain Star Party 
Location: approximately 20 miles 
north of Ellensburg, Washington 
Open: once a year in July or 
August for a three-day star party 
Note: You can get to the star party 
other ways than the directions on 

its website. Alternate routes, how- 
ever, are generally suitable only 
for four-wheel-drive vehicles. 

tfcl Oregon Star Party 
Location: Indian Trail Spring in the 
Ochoco National Forest, 45 miles 
east of Prineville, Oregon 
Open: once a year for a weeklong 
star party 

Note: This star party spreads 
across 40 acres and offers some of 
the darkest skies in the country. 
Organizers develop three observ- 
ing lists every year, each with an 
award certificate and pin. 

^ Steve Kufeld 

Astronomical Site 
Location: 2.5 acres approximately 
90 miles northwest of Los 
Angeles, California 
Open: year-round to members 
and guests of the Los Angeles 
Astronomical Society 
Note: The site offers 57 concrete 
pads with power outlets for set- 
ting up personal telescopes. 
Members can purchase one of 
these pads for a nominal fee. 
[w] i» 61 

Equipment review 

Astronomy tests Vixen's 
compact astroimaging mount 

The Polarie 

compensates for 
Earth's rotation by 
driving a standard 
ball head mount, 
which attaches to 
a camera. An 
optional tripod 
from Vixen is 
available. It costs 
$249 and comes 
with two ball 
heads, am product 

images: Astronomy. 
William Zuback 

The Polarie Star Tracker makes it easy to take long-exposure wide-field 
images, by Tom Trusock 

WF ith increasing light pol- 
lution and gas prices, 
astroimaging seems to 
be the up-and-coming 
trend in the hobby over 
the past few years. Sites that simply aren't 
good enough for visual astronomy will still 
let you produce some great photos with the 
right combination of gear and know-how. 
That's because software now allows you to 
subtract the part of your image that comes 
from light pollution. Still, there always have 
been barriers to getting started in astropho- 
tography. The deeper you get into it, the 
more it's going to cost you. 
^^ A mount is the most crucial (and 
^^ expensive) piece of hardware for an 
astroimager. When you're picking one, you 
have to choose between stability (which, for 
the uninitiated, means large, heavy, and 
expensive) and portability. You can make 

Vixen Polarie Star Tracker 

Usable: Anywhere on Earth 

Tracking rates: Wide-Field Astrophotog- 

raphy, Lunar, Solar, and Star-Scape 
Maximum load: 4.4 pounds 

(2 kilograms) 
Power: Two AA batteries or external 

power supply via mini-USB 
Battery life: About 4 hours at 68° 

Fahrenheit (20° Celsius) 
Dimensions: 3.7 by 5.4 by 2.3 inches 

(9.5 by 13.7 by 5.8 centimeters) 
Weight: 1.4 pounds (0.64 kilogram) 

without batteries 
Price: $429 

Vixen Optics 

1 023 CalleSombra, UnitC 

San Clemente, CA 92673 

[t] 949.429.6363 


things a little easier by choosing to go with 
a less demanding (but equally stunning) 
form of celestial photography — wide-field 

— but the mounts can still be rather bulky. 

Finish and features 

It was to meet this market that Vixen 
Optics introduced the Polarie Star Tracker 

— an ultraportable tracking mount 
designed for wide-field photography and 
recommended for lenses with focal lengths 
up to 100 millimeters. You can buy the 
Polarie separately, but for this review it 
came bundled as a package with a robust 
portable tripod designed with imaging in 
mind, along with two ball heads. 

The critical piece of gear, the Polarie, is 
reminiscent of a DSLR camera body in 
both size and shape, and it's quite attractive. 
Vixen placed a sighting hole (with an 8.9° 
field of view) in the upper corner to help 
align the unit with the North or South 
Celestial Pole. As someone used to lying on 
the ground when using a German equato- 
rial mount (GEM) to observe, I was grate- 
ful that the included tripod was tall enough 
to make polar alignment fairly painless. 

On the unit's side, you'll find a tilt 
meter/inclinometer (with 5° resolution) to 
get you started with polar alignment. The 
top has a "mode" dial (more on that in a 
bit), and even a shoe where you can attach 
additional accessories. The "front" of the 
unit sports a removable mounting plate, 
behind which you'll find a slot designed to 
attach to the optional polar scope — for 
those who need a more exact alignment. 

The Polarie can run via two AA batter- 
ies or by an external 4.4- to 5.25-volt 
source, and it takes that juice via a mini- 
USB plug. Vixen states that two AA batter- 
ies can run the mount for about four hours 

Tom Trusock is a seasoned skywatcher and 
techie who observes from Ubly, Michigan. 

62 Astronomy -August 2012 

► The Milky Way near Antares (Alpha [a] 
Scorpii) is a favorite wide-field sky target. For 
this shot, the imager attached his Nikon 
D700 DSLR with a 105mm Nikon lens to 
Vixen's Polarie mount. This version combines 
twelve 5-minute exposures. John a. Da™ 

Vixen Optics' Polarie Star 
Tracker is a compact mount ideal for 
wide-field astroimaging with a digital camera. 

with the maximum load of 4.4 pounds (2 
kilograms). In practice, I found the time 
varied between 90 minutes and six hours 
depending on the temperature and the 
quality of the batteries used. Imagers need 
not fear suddenly running out of juice 
because the power indicator will begin 
blinking when the batteries get low. 

The Polarie has a mounting socket 
(K"-20 thread) that will let you attach it to 
any standard photography tripod. A step- 
per motor with two bearings drives it, and 
the Polarie is usable in either the Northern 
or Southern Hemisphere. 

The tripod has four-section legs, a maxi- 
mum load bearing capacity of 6.6 pounds 
(3kg), and adjusts from 21.2 to 70 inches 
(54 to 178 centimeters) high. Collapsed, it 
measures 22 inches long (56cm) and weighs 
around 4.3 pounds (2kg) without the 
(included) pan head. The tripod has a 
geared center column and attaches using a 
setup similar to a GEM. This is a great idea 
as it's a feature that allows you to easily 
adjust the inclination. It will look familiar 
to astroimagers but somewhat less so to 
standard photographers. 

Tracking options 

The Polarie offers several different tracking 
modes you select with the mode dial: 
"Wide- Field Astrophotography" (whose 
symbol is a star); "Lunar" (symbol is a cres- 
cent Moon); "Solar" (a stylized Sun); and 

"Star-Scape" (the fraction Vi). The other 
setting (Vixen calls it "Preparation" and its 
symbol is a light bulb) is to assist in polar 
alignment. Use "Wide -Field Astrophotog- 
raphy" for deep-sky shots where you either 
won't have a foreground or where the fore- 
ground is blurred. 

The length of an unguided exposure 
before you see star trails depends on the 
focal length of the lens and the declination 
of your target object. For a DSLR with a 
24mm lens imaging a target with a declina- 
tion of 45°, you can expose for roughly six 
minutes before star trails begin to show up. 
The shorter the lens' focal length, or the 
greater the declination, the longer you can 
shoot before you run into star- trailing. 
Alternatively, shooting an object on the 
celestial equator with a 100mm lens limits 
you to about a minute of unguided expo- 
sure time before star-trailing appears. 

"Lunar" and "Solar" modes envision the 
lengths of their respective eclipses and 
allow you to track for up to four hours. The 
"Star-Scape" mode offers something of a 
compromise setting for folks who wish to 

Change the tracking mode by rotating this dial 
on the top of the Polarie Star Tracker. 

shoot the sky and also include the fore- 
ground in the frame. If you shoot with your 
camera still, the foreground will be sharp, 
but the stars will appear as trails. 

In the "Wide-Field Astrophotography" 
tracking mode, you'll see sharp stars but a 
blurry foreground. "Star-Scape" tracks at a 
slower rate, so it splits the difference 
between the (apparently) moving stars and 
the ground beneath them. 

The Polarie fits well in my camera bag, 
taking up no more room than an SLR body. 
In addition, Vixen's tripod can double as a 
photographic tripod, further reducing the 
amount of gear you have to carry. Given the 
limited amount of packing space on any 
trip, this is a useful feature. 

Wrap one up 

The Polarie doesn't have the load-bearing 
capacity to use as a tracking mount for 
visual observing, as some might want. 
What works well for a camera doesn't work 
so well for a larger telescope with a longer 
focal length. However, it's not designed for 
that, and it works superbly for its intended 
use. The build quality on the Polarie is first- 
rate, and the functionality is excellent. It 
weighs little, runs on AA batteries, and will 
conveniently pack into your luggage. 

Vixen has long been known for provid- 
ing high-quality products at good prices. If 
you're interested in wide-field astroimaging 
— say using a lens of focal length 24mm to 
85mm — and want an extremely portable 
setup, the Polarie Star Tracker fits the bill 
without breaking the bank. » 63 


by Glenn Chaple 

Accessible astronomy 

Having a disability shouldn't prevent anyone from active participation in astronomy. 



magine this. You are standing at your 
telescope waiting for the next inter- 
ested person to take a peek, when you 
notice someone in a wheelchair approach- 
ing you. All you can think of is 'What 
should I do?"' (Noreen Grice, Everyone's 
Universe: A Guide to Accessible Astronomy 
Places, You Can Do Astronomy LLC, 201 1) 

What would you do? Approximately one 
in five individuals copes with a disability 
— such as visual and/ or hearing impair- 
ments, communication challenges, or wheel- 
chair confinement. None of us is immune. 
An illness, accident, or simply the aging pro- 
cess can leave a once able-bodied person 
with a disability. And it's quite possible that 
such an individual will show up at a public 
star party you or your club is conducting. 

Having a disability shouldn't prevent any- 
one from active participation in astronomy. 
In fact, many have overcome handicaps to 
make notable astronomical contributions. In 
1783, astronomer John Goodricke, who was 
deaf/mute, was awarded the Copley Medal 
by the Royal Society of England for his work 
on variable stars. Until 1932, Edwin Frost 
was both director of Yerkes Observatory in 
Wisconsin and editor of The Astrophysical 
Journal despite having become blind 1 1 
years earlier. Blindness is no hindrance to 
modern-day astronomers — for example, 
Wanda Diaz-Merced, though blind, is an 
active radio astronomer with NASA's God- 
dard Space Flight Center in Maryland and a 
Ph.D. student at the University of Glasgow 
in the United Kingdom. 

But perhaps the most celebrated astrono- 
mer (well, physicist) with a mobility and 
communications disability is Stephen Hawk- 
ing. Despite being confined to a wheelchair 
and dependent on a computerized voice sys- 
tem to speak (a result of having contracted 
Lou Gehrig's Disease), Hawking has used his 
mathematical genius to probe some of cos- 
mology's greatest mysteries. 

Universe: A Guide 
to Accessible 
Astronomy Places, 

by Noreen Grice, 
explains how to 
help everyone see 
and enjoy the 




Noreen Grice 


Browse the "Observing Basics" archive 

Modern technology has brought research 
astronomy into our homes — a boon to 
individuals with disabilities. Computer users 
with mobility or hearing problems can 
access robotic telescopes or work on Inter- 
net projects like Zooniverse's Galaxy Zoo, 
Moon Zoo, and Planet Hunters. To support 
the upcoming Lunar Atmosphere and Dust 
Environment Explorer mission, NASA is 
asking volunteers to make meteor counts 
using FM radio receivers. Find details of this 
project, a nice fit for visually impaired space 
enthusiasts, at 

But back to the original question. What 
would you do should a person in a wheel- 
chair approach you at a star party? Noreen 
Grice has some ideas. She became an 
advocate of astronomy for visitors with 
disabilities after a planetarium show she 
conducted for a group of children who 
were blind. An assessment of the program 
according to the kids? "It stunk!" 

Spurred by the incident, Grice began to 
research strategies for presenting astronomy 
to individuals with a variety of disabilities. 
Ultimately, she established You Can Do 
Astronomy LLC — a company whose mis- 
sion is to make astronomy and space sci- 
ence accessible to people of all abilities. Her 
book Everyone's Universe: A Guide to Acces- 
sible Astronomy Places is a must-read for 

anyone involved in astronomy outreach 
and should be in the possession of every 
astronomy club and science facility. 

Everyone's Universe is designed to edu- 
cate both astronomy clubs and partici- 
pants with disabilities. Suggestions for 
accessible outreach efforts include eyepiece 
extenders for those using wheelchairs, tac- 
tile books like Grice's Touch the Stars 
(National Braille Press, 2002) for readers 
who are visually impaired, picture boards to 
assist individuals with communication chal- 
lenges, and simple paper and pen or iPad to 
interact with a person who cannot hear. 
Everyone's Universe also provides a state-by- 
state listing of accessible astronomy facilities, 
such as planetariums and observatories. 

But why wait for a person with a disabil- 
ity to show up at your star party? Be proac- 
tive and organize an accessible star party in 
your community! In Everyone's Universe, 
Grice spotlights Project Bright Sky, devel- 
oped by the Pomona Valley Amateur 
Astronomers (PVAA) in California. 
Through this project, the PVAA conducts 
private star parties for those who are visually 
impaired and offers tactile astronomy classes 
at local Braille institutes. For more on You 
Can Do Astronomy and Project Bright Sky, 
visit and, respectively. 

As we strive to infuse the excitement of 
astronomy into the public, we mustn't 
neglect the 20 percent of the population 
suffering from some kind of disability. Who 
knows? That person approaching your tele- 
scope might be a potential contributing 
member of your astronomy club, possibly 
even a future scientist. You can help make 
the universe more accessible! 

Questions, comments, or suggestions? 
Email me at Next 
month: some lunar letters. Clear skies! <* 

This article is dedicated to Ellie Isaacs, whose 
pen-on-paper rendering of Stephen Hawking 
appeared on page 1 of the May 2012 issue of 
Astronomy magazine. 

64 Astronomy -August 2012 


ImagingtheCosmos ^M 

by Tony Hallas 

HDR Toning/ 7 part 2 

Learn how to tweak the details in your images to achieve a fantastic look. 

In my previous column, I went over the 
basic controls of Adobe Photoshop CSS's 
"High Dynamic Range (HDR) Toning." 
Now, it's time to fine-tune. 

To fully understand HDR, it helps to 
know why it was invented. As digital imag- 
ing evolved, it became easy to capture 
information beyond what a single frame 
can depict. When Photoshop creates a huge 
32-bit image — by combining data from 
the deepest shadows to the brightest high- 
lights — a problem arises. How do you 

helpful to have your first step be simply 
using both sliders to make the highlights 
look normal again. 

The "Radius" setting under "Edge Glow" 
works similar to the "Radius" setting in 
"Unsharp Masking," another image manip- 
ulation technique: Selecting smaller pixel 
amounts emphasizes the fine detail, while 
working with large numbers of pixels 
emphasizes the overall image. I usually 
leave the "Strength" of "Edge Glow" around 
0.50, unless the image is unresponsive. 

It's easy to overprocess your photos 

with this powerful tool. Your goal is to 

maintain the "natural" look of each 

image for the best results. 

bring all these tonal values down to a more 
limiting 16- or 8-bit image without losing 
too much detail? If we could go into this 
huge image and enhance the local detail 
elements in it, then when we reduce bit 
depth (and lose data), the major detail will 
still be there after the loss. 

It turns out this same idea applies to 
well-made astroimages, which possess good 
detail from the shadows to the highlights. 
The better the data you start with, the more 
"HDR Toning" can do for your image. It will 
analyze your image and attempt to enhance 
the subtle detail through the process of 
"local micro contrast enhancement." Let's 
examine the HDR controls more closely. 

First of all, know that whenever you 
process an astroimage in HDR, the high- 
lights are likely to wash out right away. 
Not to worry: the "Gamma" and "High- 
light" sliders under "Tone and Detail" 
work well together to bring them back. It's 


Browse the "Imaging the Cosmos" 
archive at 

"Detail" (also under "Tone and Detail") 
is like a multiplier of the "Edge Glow" 
effect. Watch what happens when you set 
the "Edge Glow" "Radius" slider to different 
settings while moving the "Detail" slider 
back and forth. Remember, this is a power- 
ful setting, and it requires discretion. You 
want to enhance the detail in your image, 
but not make it obvious how you did it. 

Once you are satisfied with your set- 
tings, go back and fine-tune the "Gamma" 
and "Highlight" settings one last time. You 
want as much "Gamma" (midrange con- 
trast) as your image can support while 
working in conjunction with the "High- 
light" slider to keep the image's highlights 
from blowing out. 

One of the side effects of "HDR Toning" 
is emphasizing the noise structure, or visual 
static, along with the other detail in your 
image. To fix this, simply use a mild noise 
reduction application such as Neat Image or 
Noise Ninja afterward — and possibly 
before, if your image is noisy to begin with. 
Excessive noise can "distract" the HDR 

The Horsehead Nebula appears here after 
basic processing but before "High Dynamic 
Range (HDR) Toning" (top), after good use of 
"HDR Toning" (middle), and after too much HDR 
use. It can be easy to overdo it, leaving an 
astroimage looking stark and unnatural, but 
correctly using "HDR Toning" can improve an 
already great image. TonyHaiias 

software from the image's true tonal values. 
It bears repeating that it's easy to overpro- 
cess your photos with this powerful tool. 
Your goal is to maintain the "natural" look 
of each image for the best results. 

"HDR Toning" may seem intimidating 
at first, but if you experiment with the con- 
trols, it will soon start to make sense. (For 
more details, visit In 
other words, the best way to understand 
HDR is to use it! » 65 

Deep-sky Showcase 

Astronomy's editor sketches two of his favorite objects, by David J. Eicher 

The Eagle Nebula 
and NGC 7023 

The Eagle Nebula sketched by David J. Eicher 
using an 8-inch f/1 Celestron SCT at 70x. 

The Eagle Nebula (Ml 6) 

Serpens Cauda contains one of the most 
unusual and complex regions of ionized 
hydrogen in our galactic neighborhood 
- the Eagle Nebula (M16). This large 
emission nebula is centered on a 
bright star cluster containing 60 
stars of 8th magnitude and fainter 
in an area 25' across. The star 
cluster makes for a fine binocular 
sight and, at 6th magnitude, is 
just visible to the naked eye from 
a relatively dark site. 

M16's star cluster is bright and 
easy to see; the challenging aspect 
of this object is to spot the glow 
from the gas that produced the cluster 
and now fluoresces under strong gusts 
from hot stellar winds. The nebulosity has 
a low surface brightness, and its visibility is 
further hindered by the presence of several 
bright stars in the field; through an 8-inch 
scope at low power, it appears as a milky, 

Designations: Ml 6, NGC 661 1 
Position: 18h19m, -13°48' (2000.0) 
Constellation: Serpens Cauda 
Magnitude: 6.0 
Size: 35' by 28' 
Distance: 5,600 light-years 

greenish -gray light. Larger scopes show 
more nebulosity, channels of dark nebulae 
interlaced throughout, and the dark glob- 
ules that are collapsing into protostars. The 
nebulas low surface brightness means 
observing it on a moonless night is essen- 
tial; it also makes it difficult to use high 
magnifications. A good nebula filter often 
helps with contrast, making the faint out- 
lines of the Eagle easier to see. 

Designation: NGC 7023 
Position: 21 h02m, 68°10' (2000.0) 
Constellation: Cepheus 
Magnitude: 6.8 

Size: 18' 

Distance: 1,300 light-years 

David J. Eicher is the editor of Astronomy. 
He has observed and sketched deep-sky objects 
for 36 years. 

NGC 7023 

The west-central portion of the constella- 
tion Cepheus holds an unusual object — 
the faint reflection nebula NGC 7023, 
sometimes called the Iris Nebula. Most 
glowing gas clouds in the sky shine through 
the process of ionization — excited atoms 
kick off a photon and glow like a fluores- 
cent lamp. By contrast, reflection nebulae, 
which appear bluer as opposed to reddish 
emission nebulae, glow softly simply by 
reflecting the tenuous light of bright stars 
that lie nearby. 

As is the case with many reflection neb- 
ulae, NGC 7023 is fairly large and diffuse. 
Measuring 18' across and dimly lit by a 7th- 
magnitude star, NGC 7023 demands at least 
a 6-inch telescope for viewing even under 
dark skies. With a 10-inch or larger instru- 
ment, the nebulosity is easy to observe but 
appears completely featureless — a faint 

NGC 7023 sketched by David J. Eicher using an 
8-inch f/10 Celestron SCT at 50x. 

glow centered around the star that allows 
us to see it. A larger scope brings out more 
shape in the nebula but fails to reveal much 
more in the way of features. » 

66 Astronomy -August 2012 

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Quest for the ' 


The search for the first structures 

in the universe has baffled 

astronomers for decades. But 

telescopes now on the horizon 

promise to shed new light. 



Brian May 

A life in science 
and music 

Black holes in 
our backyard 

At least two 
dozen of these 
objects lurk 
within the Milky Way 



I Astronomy's third annual 
Star Products 

I Wander the wonders in the 
King's constellation 

I You should observe the 
Full Moon 


magazine w 

70 Astronomy -August 2012 

■ i reader 

gallery 71 

LBN 468 is a region of nebulosity in Cepheus that lies near the Iris Nebula (NGC 7023). At the 
upper left, you can see Gyulbudaghian's Nebula (arrow), a triangular patch surrounding the star 
PVCephei. (10-inch Boren-Simon PowerNewt astrograph atf/2.8, SBIG ST-8300M CCD camera, 
LRGB image with exposures of 62, 5, 5, and 5 minutes, respectively) • Kfir Simon, Gan Yavne, Israel 

Planetary nebula Abell 61 in Cygnus interacts 
with the interstellar medium, which explains the 
bright, distinct rim to the upper left compared 
to the fainter, disrupted rim to the lower right. 
(16-inch RC Optical Systems Ritchey-Chretien 
reflector at f/8.9, Apogee U16M CCD camera, 
Ha/OIII/RGB image with exposures of 330, 210, 
20, 20, and 20 minutes, respectively) • Don 
Goldman, Orangevale, California 

IC 131 1 (just to the right of center) is a magnitude 13.1 star cluster that 
lies in a region of sky filled with emission nebulosity. You'll find it 2.3° 
west-northwest of Sadr (Gamma [y] Cygni [not shown]). (7.2-inch 

Takahashi E-180 hyperbolic astrograph, SBIG ST-10XME CCD camera, 
HaLRGB image with exposures of 1 20, 1 5, 1 5, 1 5, and 1 5 minutes, 
respectively) • Daniel B. Phillips, Oceanside, California 

72 Astronomy-August 2012 

Send your images to: Astronomy Reader Gallery, P. 0. Box 1612, 
Waukesha, Wl 53187. Please include the date and location of the image 
and complete photo data: telescope, camera, filters, and exposures. 
Submit images by email to 

■ | reader 


The Needle Galaxy (NGC 4565), an edge-on spiral in Coma Berenices, 
shines at magnitude 9.6. A dust lane runs the entire length of this object, 
masking much of the arms' brightness. If your telescope's aperture is 1 2 
inches or more, try to view the magnitude 1 3.5 galaxy NGC 4562. From the 

Needle Galaxy, this faint spiral lies 13' southwest (lower right in this 
image). (14.5-inch RC Optical Systems Ritchey-Chretien reflector at f/8, 
Apogee U16M CCD camera, RGB image with exposures of 220, 140, and 
240 minutes, respectively) • Mark Hanson, Madison, Wisconsin 73 

The Cosmic 

All things high, low, weird, and wonderful in astronomy and space science, by Bill Andrews 

Political science 

Arizona governor Jan Brewer 
vetoes a bill that would have 
destroyed the state's dark skies, 
thanks to awareness efforts by 
amateur astronomers. My faith 
in the system is restored! 


Keepin' it cool • 

A Slate article asks, "Can 
John Carter make the red 

planet cool again?" Sounds 
like someone hasn't seen 

Astronomy's August lineup! 

The perfect name 

The 43rd Lunar and Planetary 
Science Conference features a 
presentation on Mars by French 
scientist John Carter. Man, stu- 
dios are pulling out all the stops 
for their promotions! 


Andre in the sky 

Beatles tribute band Love & Mersey 
honors Dutch astronaut Andre 

Kuipers with the song "Back at the 
ISS (yeah)" — like it wasn't cool 
enough just being an astronaut. 

Starry Ocean 

NASA's Goddard Space 

Flight Center creates an 

animation showing 

off surface ocean 

currents — and Earth's 

post-impressionist phase. 

Totally awesome 

The Royal Astronomical 

Society releases a story 

about comets and the Sun 

with the headline, 

"Supersonic snowballs in 
hell."Wow, I hope they put 

out an album sometime. 

Science party! 

This month's good news 
Astronomers announce the pos 
sibility of billions of habitable 
planets in our galaxy, and a 
NASA official predicts the dis- 
covery of a "goldilocks planet" 
within the next two years. 


NASA finds the 

perfect host for a 

public service 


about everyday 

technologies the 

agency pioneered: 

equally derivative 

musician Will. 

Birds ... in ... space! 

ISS astronaut Don Pettit 
helps demonstrate 
trajectories for the new 
game Angry Birds Space, 
developed with NASA's 
help. The ISS proves its 
usefulness once again. 

Dione's freshness 

NASA announces that 
its Cassini spacecraft 
"sniffed" the atmo- 
sphere of Saturn's 
moon Dione, finding a 
"Hint of Fresh Air" 
which must be nice 
after all those years in 
stuffy space. 

Murderous Moon? 

Texas State University-San 
Marcos asks, "Did the moon 

sink the Titanic?" Short 
answer: no. Long answer: 


1 -click history 

Amazon founder Jeff Bezos locates 
and plans to retrieve the main 
engines from the first stage rocket 
of Apollo 11, with NASA's blessing. 
No word yet on shipping costs. 


Astronomers study- 
ing exploding stars 
describe some as 
"showing such 
good table man- 
ners." Let that be a 
lesson to anyone 
struggling with gas 
during dinner. 

Loony website 

The website 
shows off footage from a mission to 
Jupiter's moon Europa. Either it's 
promoting the movie The Europa Report, 
or NASA really got scooped. 

Enigmatic excitement 

The U.S. Air Force indefinitely 
extends the mission of its 
X37-B — a secret, unmanned, 
experimental space plane 
called "game-changing" by 
the head of the Air Force 
Space Command. 
So, uh, yay 

Personifying planets 

NASA's Jet Propulsion •"" 
Laboratory releases 
an article titled "The ^^ 
Many Moods of Titan," ^^^ 
presumably to contrast it 
with that one-note jerk Uranus. 

Ultra ultra screen 

Stanford University animations promise to 
bring the universe "to the big screen." I knew 
movie screens were getting bigger, but I'm 
still impressec 

Anti-science party 

A scientific study shows that 
conservatives' trust in science 
has fallen precipitously in the 
past 25 years. Evolutionists, 
climate scientists, and FDA 
scientists respond, "No kidding!' 

( ^ 

74 Astronomy-August 2012 


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The LX600 is a simple to operate, portable package that makes taking great astrophotos as easy as focusing 

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► StarLock The LX600 integrates a unique star tracking and object finding system into the 

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► Portability While you can achieve remarkable visual and imaging results from a 
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Southern Sky 

Mercury at its best 

As October begins, three 
naked- eye planets grace the 
western evening sky. The 
brightest is Mercury, a nor- 
mally inconspicuous object 
that puts on its finest show 
of the year this month. The 
innermost planet lies low 
in the twilight during early 
October, appearing 8° above 
the horizon 30 minutes after 
sunset. (Use binoculars if you 
can't spot it with naked eyes.) 
Mercury climbs higher and 
into a darker sky as it draws 
away from the Sun this 
month. When it reaches great- 
est eastern elongation Octo- 
ber 26, it appears 17° high a 
half-hour after the Sun goes 
down and doesn't set for 
another 90 minutes. 

The view of Mercury 
through a telescope changes 
quickly as October progresses. 
The planet spans 5" and shows 
a fat gibbous phase during the 
month's first two weeks. It 
grows to 7" and appears about 
60 percent illuminated by 
greatest elongation. Its phase 
dwindles to half-lit by Octo- 
ber's final evening. 

Saturn accompanies Mer- 
cury in the twilight during 
October's first week. The two 
pass 3° from each other on 
the 6th. Mercury then shines 
at magnitude -0.3, a full 
magnitude brighter than Sat- 
urn. Unfortunately, the low 
altitude renders the ringed 
planet uninspiring when 
viewed through a telescope. 

Mars resides much higher 
in the evening sky. Shortly 
after midmonth, the Red 
Planet passes just north of 
Antares, the lst-magnitude 

red giant star that marks the 
Scorpion's heart. It's fascinat- 
ing to see the two side by side. 
The star's name means "rival 
of Mars," and the objects' 
proximity gives you a good 
chance to compare their simi- 
lar colors. A telescope reveals 
Mars' shimmering disk, which 
measures just 5" across and 
shows no detail. 

Not long after Mars sets, 
you can find Jupiter rising 
in the northeast. The giant 
planet currently lies among 
the background stars of Tau- 
rus, between the Bull's horns. 
Jupiter's 45"-diameter disk 
shows lots of detail through 
a telescope, although its 
northerly declination means 
it doesn't climb higher than 
about 30°. For the best views, 
wait until it reaches its peak 
in the northern sky shortly 
before dawn. 

Even a small scope reveals 
two dark belts that straddle 
the giant planet's equator. 
Under good conditions, 
observers typically see an 
alternating series of dark belts 
and bright zones. Also keep 
an eye out for the planet's four 
bright moons, which shift 
position from night to night. 

Brilliant Venus hangs low 
in the east before dawn. It 
passes close to lst-magnitude 
Regulus in Leo the Lion dur- 
ing October's first week. At 
magnitude -4.1, however, the 
planet shines more than 100 
times brighter than the star. 
Although Venus lies 40° from 
the Sun early this month, it 
appears quite low in the sky 
because the ecliptic — the 
path of the Sun across the sky 

that the planets also follow 
closely — makes a shallow 
angle to the eastern horizon 
on spring mornings. 

The best telescopic views 
of the planet this month come 
shortly after twilight begins. 
In early October, the planet 
spans 16" and appears about 
70 percent illuminated. By 
month's end, Venus' disk 
measures only 13" across 
and shows an 80-percent-lit 
gibbous phase. 

The Moon occults Jupiter 
on October 5/6 for residents 
in southern Australia and Tas- 
mania. From Perth, the planet 
disappears behind the Moon's 
bright limb at 20h52m Uni- 
versal Time (UT) October 5, 
which is 4:52 a.m. local time 
October 6. Jupiter reappears 
at 21h51m UT, almost pre- 
cisely the time of sunrise. 

The starry sky 

In 1804, Karl Ludwig Harding 
(1765-1834) discovered the 
third asteroid, Juno, while 
working at Johann Schroter's 
observatory in Germany. To 
deep-sky observers, however, 
Harding's main claim to fame 
is the discovery of the Helix 
Nebula (NGC 7293). He 
found this object while 
compiling a catalog of some 
120,000 stars. 

The Helix lies in southern 
Aquarius, a dim region that 
climbs high in the northern 
sky on October evenings. You 
can find it about 10° north- 
west of lst-magnitude Fomal- 
haut, the brightest star in 
Piscis Austrinus. As you close 
in on the area, look about 
1° west of 5th-magnitude 

Upsilon (i>) Aquarii. The neb- 
ula lies one-quarter of the way 
from Upsilon to the similarly 
bright star 41 Aqr. 

The Helix belongs to a 
class of objects known as 
planetary nebulae. These 
objects form near the end of a 
Sun-like star's life. As the star 
starts to run out of nuclear 
fuel, it swells into a red giant. 
The bloated object has at best 
a tenuous hold on its outer 
layers, and pulsations can 
drive off this gaseous material. 
The star's core remains as a 
white dwarf — a hot remnant 
that radiates lots of ultraviolet 
light. This radiation excites 
the atoms in the gaseous enve- 
lope and causes them to glow. 

Although the Helix has an 
impressive total magnitude of 
about 7, it is difficult to spot 
because its light spreads out 
over such a large area. The 
nebula spans 15' by 12', which 
makes it nearly half the diam- 
eter of a Full Moon. 

Under a dark sky, the Helix 
shows up through 7x50 bin- 
oculars. Still, the nebula is far 
more impressive through a 
telescope. Just make sure to 
use low power so you have a 
fairly wide field of view. The 
first time I viewed the Helix, 
I was taken aback to realize 
that it filled much of the tele- 
scope's field. 

If you'd like a challenge, see 
if you can spot the nebula's 
central white dwarf star. 
Glowing dimly at magnitude 
13.4, it's beyond the range of 
the smallest telescopes, but 
20-centimeter or larger 
instruments show it under 
good conditions. '* 

The all-sky map shows 
how the sky looks at: 

10 p.m. October 1 
9 p.m. October 1 5 
8 p.m. October 31 

Planets are shown 
at midmonth 





1 w+; 

\\ +«3S N — ^ J *; 

• SNV1DO / 

/' // 

/* /J 

I £ o. / • / * 

Open cluster 
Globular cluster 

Diffuse nebula 

3.0 <J>- Planetary nebula 


5.0 O Galaxy 



fiis map: This map portrays the sky as seen near 30° south 
ted inside the border are the four directions: north, south, 
id west. To find stars, hold the map overhead and orient it 
j a direction label matches the direction you're facing. The 
stars above the map's horizon now 
match what's in the sky. 

Star colors: Stars' true colors depend on 

surface temperature. Hot stars glow 

blue; slightly cooler ones, white; 

intermediate stars (like the Sun), 

yellow; followed by orange 

and,ultimately, red. Fainter 

stars can't excite our eyes' 

color receptors, and so 

appear white unless 


October 2012 

Calendar of events 

1 Mercury passes 1 .8° north of Spica, 

3 Venus passes 0.1° south of Regulus, 

4 Jupiter is stationary, 1 4h UT 

5 The Moon is at apogee (405,1 60 
kilometers from Earth), 0h43m UT 

The Moon passes 0.9° south of 
Jupiter, 21 hUT 

6 Mercury passes 3° south of Saturn, 

7 The Moon passes 0.9° south of 
asteroid Ceres, 5h UT 

8 Last Quarter Moon occurs at 

12 The Moon passes 6° south of Venus, 

15 New Moon occurs at 1 2h03m UT 

1 7 The Moon is at perigee (360,672 
kilometers from Earth), 1h00m UT 

The Moon passes 1.3° north of 
Mercury, 2h UT 

18 The Moon passes 2° north of Mars, 

20 Mars passes 4° north of Antares, 

The Moon passes 0.08° south of 
Pluto, 14hUT 

21 Orionid meteor shower peaks 
Asteroid Vesta is stationary, 7h UT 

22 First Quarter Moon occurs at 
3h32m UT 

24 The Moon passes 6° north of 
Neptune, 16hUT 

25 Saturn is in conjunction with the Sun, 

26 Mercury is at greatest eastern 
elongation (24°), 22h UT 

27 The Moon passes 5° north of Uranus, 

29 Full Moon occurs at 19h49m UT 

31 Asteroid Ceres is stationary, 21 h UT 


For definitions of terms, log onto m/g lossa ry. 


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